The Curious Case of the Disappearing Image

During our first live test of Rogo, we were somewhat alarmed when the students pointed out that one of the questions was missing an image. Although far from ideal, it was thankfully not disastrous, as it was noticed fairly early on and we were able to print out a copy of the image for all the students.

The question is, what happened to this image? The paper was checked thoroughly against the QuestionMark Perception version of the paper immediately after it was imported, so it would have been spotted at that point had it not come through in the import. However, I clearly did not check the paper thoroughly enough immediately before the exam, as the image was not there.

So the image was lost from the question between it being imported into Rogo and the paper being taken. To find out when and why, I reimported just this question. The image is there in the QTI XML export from Perception, and was there in the question immediately after import. However, after saving the question from the edit screen, without having made any changes to the question, the image had disappeared. The table cell that should contain the image was left just containing an  .

We presumed there was something in the imported HTML that was causing this to occur. Initially we thought it might be that there was no closing tag for the <IMG …> (nor a closing slash at the end of the tag), but adding this made no difference, and there were other questions that have the same lack of closing tag and there were no problems with these. On closer inspection of the html for the questions, we noticed that there was a span in the question intro in the faulty question that was not there in any others. This span contained some attributes that came from MS Word:

<SPAN style=”mso-bidi-font-family: Arial; mso-hansi-font-family: Arial” lang=EN-GB><STRONG>diaphragm <BR></STRONG></SPAN>

Removing the span altogether fixed the problem, so we drilled down in order to identify what aspect of the tags was causing it. We looked into the following:

  • The <br> inside span the span? Moving it outside made no difference
  • No quotation marks around EN-GB? Adding them made no difference
  • The lang attribute? Removing it made no difference
  • Non-standard CSS properties in style attribute? Removing the styles fixed the problem

Although it is nice to have found the specific cause, there is no reason for this span to exist at all, so we have removed it completely from the imported version. Hopefully questions containing spans such as this will be few and far between, but since many questions are copied in from Word, care needs to be taken, as it seems that the Rogo text editor, not unusually, does not like them.

For future imports, a quick find/replace through the QTI XML exports when we transfer questions en masse from Perception to Rogo should enable us to remove problematic spans. We will have to do some modification of the XML anyway (e.g. changing the path to images), so it will not be much more work to sort this out as well. I have also blogged about other issues relating to importing questions.

Importing Questions into Rogo

In preparation for our first running our first live test of Rogo, we needed to get an exam paper that had been created in Questionmark Perception into Rogo. This seemed simple enough, simply by exporting the QTI XML from Perception and importing it into Rogo. This generally worked reasonably well, but there were a few issues that had to be dealt with:

  • Not unsurprisingly, images needed special attention. The links to the images in Perception (e.g. “%SERVER.GRAPHICS%topicresources/1065007843”, where the number at the end is the topic id) were replaced (using a blanket find/replace) with “/media(/subdirectorypath)”, and the images copied into the appropriate subdirectory.
  • There were some issues with tables where an image was shown side by side with the answer options, which required a hack in Perception. For some questions there were problems in the HTML in Perception (left over from the dark ages), so fixing the HTML in Perception fixed the import problems relating to this.
  • EMQ feedback – the general question feedback from Perception is given as the feedback for all stems in Rogo, which does not have general feedback for EMQs. This can be fixed by removing the feedback from all except the last question, so that it just appears at the end of the responses. Alternatively, the feedback can be split up to give each stem its own feedback. Either of these options would be laborious for large numbers of questions, so the best long-term alternative may be to alter the import code to deal with this.
  • MCQ feedback – when importing MCQs (including those created in Rogo, exported and imported back in without any modification), in which only general feedback is provided, the general feedback is put in the answer feedback for each answer and general feedback is left empty. This has been added to the Rogo Trac system (#683,
  • Correct answers for EMQs – after importing all the correct answers are set to A. This is also the case if a question is created in Rogo, exported from Rogo and imported back in. This issue was added to Trac (#682, and has now been fixed by the Rogo team, presumably for a future release. For this assessment, fixing this was simply, but annoyingly, a case of going through all the questions and changing the correct answers.
  • Rogo does not have a multiple MCQ question type, i.e. several MCQs that share the same stimulus and so are combined into a single question, so that it looks like an EMQ, but there are different answer options for each stem. Such questions are recognised as Matrix questions by Rogo when they are imported, but this format is not appropriate. There is no way of modifying an EMQ in Rogo so that subsets of the answer options are only available for certain stems. We have a large number of questions of this format, and currently the only option is to separate them out into MCQs, which is not a sustainable solution. Therefore, we may need to create a multiple MCQ question type, which hopefully would not be too difficult using the EMQ question type as the basis.

Having fixed all these problems, it seemed as though we had an exact copy of the assessment, with everything working as it should. The only difference between the questions as far as the students were concerned was that the multiple MCQ question (there was only one of this type in this paper) was split into 5 separate MCQs.

However, while running the assessment, we were to come across the Curious Case of the Disappearing Image, which, it turned out, was caused by a problem related to importing.

Safe Exam Browser

Because Rogo doesn’t itself come with a secure browser it prompted us to look for something third-party. A helpful pointer from Farzana Khandia from Loughborough on the very helpful QUESTIONMARK@JISCMAIL.AC.UK list, led us to Safe Exam Browser (SEB). This is a fantastic bit of free software which has a number of advantages over QuestionMark Secure (QMS), including:

  1. Once installed by an administrator, SEB uses a Windows service to prevent access to the Task Manager, Alt-Tab, etc. This means a typical computing lab ‘user’ will be able to run it with no further work. In contrast, QMS requires that typical user to be given read/write permissions on a number of registry keys – a fiddly process and one which upsets many IT officers.
  2. SEB is launched from a desktop shortcut and then calls the assessment server (or other system specified in an ini file before installation). It then carries on running until an IT officer closes it down. QMS starts and stops when a secure assessment is opened and submitted respectively. This leaves the machine unsecured once a participant has submitted.
  3. SEB allows administrators to allow access to ‘Permitted Applications’  such as  the system calculator and Notepad – this is not possible in the version of QMS that we are using.

The only disadvantages over QMS that we have discovered so far are:

  1. The requirement to enter a key sequence to close down the SEB slightly increases the time required to reset computers between sittings of students.
  2. If the machine crashes or is switched off while SEB is running, a bat file needs to be run to re-enable the functions disabled by SEB i.e it only re-enables them itself when it is closed normally.

We’re now considering whether we could use SEB instead of QMS, even with Perception-delivered assessments as it would save us the extra annual subscription for support on that proportion of our licence.


The importance of paper type in Rogo

One of the problems which very nearly forced us to abandon our first test of Rogo yesterday was our lack of understanding of the importance of paper ‘type’ in assessment delivery in Rogo and, arguably, the degree to which we are used to the way that QuestionMark Perception does things.

Test Type Feedback? Restart? Fire Exit? Multiple Attempts? Review Previous attempts?
Self-Assessment Test Yes, granular control No No Yes Yes
(Quiz) (Yes) (Yes if SAYG) (n/a) (Yes) (Yes if enabled)
Progress Test No – but options shown in Assessment properties screen. Yes No No No
(Test) (User decides) (Yes if SAYG) (n/a) (Yes) (Yes if enabled)
Summative No Yes Yes No No
(Exam) (No) (Yes if SAYG) (n/a) (Yes) (Yes if enabled)

The three main assessment types in Rogo (with a comparison with Perception in brackets)

In Questionmark Perception, ‘Assessment Type’ is a convenience method for setting various parameters of assessment delivery. However, the parameters are set explicitly and are visible to administrators. They are also all individually configurable regardless of assessment type.  In Rogo, paper type is considerably more important as, although it sets very similar parameters to those in Perception, they do not seem then to be independently configurable or, crucially, to be visible to administrators. As a result it is very easy to inadvertently, but radically, change the way in which an assessment is delivered. Or as we found, it was not possible to deliver the assessment in the way required at all.

We wanted to be able to deliver a formative paper under exam conditions which would display marks and feedback to students at the end but which would also allow students to restart their assessment if something went wrong before they had finished. We began by setting paper type to ‘Progress Test’ as this gave us the feedback we required but then realised this wouldn’t allow students to restart in the event of a hardware failure. So we tried ‘Summative’ but, despite having ticked the two feedback tick boxes, no feedback appeared. Luckily, since we were only testing the system, we could nip in and alter the offending bit of code (paper/finish.php, line 234) to allow feedback with a summative paper:

$show_feedback = true;

but this wouldn’t be acceptable on a production system.

It seems to me that, in this respect, the QuestionMark Perception model is better – paper type should help by suggesting appropriate settings not by constraining how an assessment can be delivered.

Hurray – Rogo performed brilliantly in its first real test at Oxford

Monday 23rd April saw a total of 73 first year medics, half of each of two sittings, take their voluntary assessment in Organisation of the Body on Rogo while the other half of each sitting used QuestionMark Perception as normal.

After a longer than usual introduction (see below), to explain the differences between this and ‘normal’ online assessments, we started the group in two halves, approximately 10s apart. There was no perceptible delay despite the fact that both application and db are running on one >3yr old server.

This was a great outcome given that we very nearly abandoned this test of Rogo at the last minute because of serious potential problems – one to do with server errors after amending ‘locked’ questions, the other to do with paper ‘types’. Disaster was averted by my colleague Jon Mason, who spotted and corrected both problems just in time.

Extra instructions at the beginning of the assessment:

“You are in the very privileged position today to be the first group of students to try out a new assessment system, Rogo. This works in more or less the same way as the ‘normal’ system, Perception, except that:
1. The assessment will not submit itself at the end, we will ask you to click ‘Finish’ after 45 minutes;
2. Because it doesn’t time itself, I will tell you when there are 5 minutes remaining to you. There is a clock at the bottom left of your screen – I suggest you make a note of your start time as you would with a normal exam.
3. The questions will be presented on 6 ‘screens’ which you can move between (backwards and forwards) using the controls at the bottom right.
4. When you go back to a screen you have previously visited, unanswered questions will be highlighted in pink.
5. Please make sure you do not click the ‘Finish’ button until you have answered all questions as you will not then be able to return to them.
6. We have appended three questions to the end of the assessment which ask for your thoughts on this new software. You do not have to answer these but we would be grateful for any feedback you can give us – it will help us to decide whether this is a viable alternative to the existing system.”


Question Analysis – Difficulty/Facility and Discrimination


This is simply a measure of the proportion of students that answered a question correctly and has a value of between 0 and 1. It is calculated by taking the sum of the actual marks for each candidate and dividing it by (the maximum multiplied by the number of candidates).

It is often referred to as difficulty, but should probably be known as facility, as a value of 0 means that no-one answered the question correctly, and a value of 1 means that everyone answered the question correctly.

General wisdom seems to be that questions with facility values of around the pass mark for the assessment (e.g. pass mark = 70%, facility = 0.7) will give the most most useful information about the candidates.


The purpose of item discrimination is to identify whether good students perform better, worse or the same as poor students on a question. Based on Kelley (1939), good and poor students are defined by taking the top and bottom 27% based on overall assessment mark.

Discrimination for a particular answer option is then calculated by subtracting the fraction of the bottom group who gave the answer from the fraction of the top group who gave the answer. So:

  • A positive item discrimination means a higher proportion of people in the top group chose the answer than in the bottom group. A high positive value for the correct answer generally means the question is a good discriminator, which is what we want (but is very difficult to achieve!). A positive discrimination for an incorrect answer may suggest an issue, but could equally just mean that it is a good distractor.
  • An item discrimination of 0 means the same number of people from each group gave the answer, so the answer doesn’t discriminate at all. Questions where everyone got the correct answer will always have a discrimination of 0.
  • A negative item discrimination means a higher proportion of people in the bottom group chose the answer. This would be expected for an incorrect answer. A negative discrimination on a correct answer may indicate something is wrong, as more able students are choosing an incorrect answer.

To make a question a good discriminator, the correct answer should have a high positive discrimination, and the incorrect answers should have a negative discrimination.

Reporting in Rogo

Currently, reporting in Rogo is only assessment-based. The following reports are available:

  • Class Totals (available as HTML, CSV or Excel) – scores for individuals
  • Frequency & Discrimination (U-L) Analysis (HTML only) – item analysis with frequencies, item difficulty and discrimination value
  • Export responses as CSV file – question by question responses
  • Export marks as CSV file – question by question marks

Class Totals

Example of Class Totals output
Example of Class Totals output (click to view full size)

The class totals output, which is available as HTML, CSV of Excel formats, shows individual results for students who have taken the paper. The table of results has the following headers:

  • Name
  • Student ID
  • Course
  • Mark
  • Percentage
  • Classification (Pass, Fail etc)
  • Start Time
  • Duration
  • IP Address
  • Room
  • Extra

It also produces a histogram for the percentage marks, and a scatter plot of percentage against duration (time taken). Summary statistics, including measures of central tendency, standard deviation and percentiles are also produced.

Frequency & Discrimination (U-L) Analysis

Example of Item Analysis Output
Example of Item Analysis Output (click to view full size)

This analysis is produced on an item by item basis, and is only available in HTML format. It shows the percentage of total respondents who chose each option, as well as the percentage of respondents from the top and bottom groups (the top and bottom 27%, based on overall assessment mark) who chose the correct option.

The p-value, or ‘difficulty’ (actually facility, as 0 = no-one answered the item correctly and 1 = everyone answered the item correctly), is shown, as is the discrimination, d. See the Question Analysis – Difficulty/Facility and Discrimination post for more on this.

At the moment it is not possible to obtain aggregated statistics about a question that has been used in multiple exams. However, the Rogo team have said that this is something that they are looking at for the future.

Export responses/marks as CSV file

The responses export provides a CSV (comma-separated values) file showing the response that each candidate gave,  as a number that corresponds to the option numbers in the question editor (for EMQs/MCQs). It also gives the correct answer for each question/item.

The marks export does the same, but giving the candidate’s mark for each question/item.

Other Reports

It is also possible to output a “Learning Objective Analysis” report, but we have not looked into this yet, as we have not mapped any assessments/questions to learning objectives.

There are also reports available called “Internal Peer Review” and “External Examiners”, but these, I presume, relate to comments/analysis produced during the process of creating the assessment, rather than to student results/question performance.

CSS – Start values in ordered list

When trying to specify the start value for an ordered list, i.e. to make it start from 4 rather 0, I found that the “start” attribute, e.g. <ol start=4>, had been deprecated in HTML 4 and that it should be done using CSS. However, the CSS is more complicated than it seems it should be for what is a relatively straightforward task. It also seems strange that it should be part of CSS, as the start value is not really a style consideration.

Thankfully, in the HTML5 specification – – the start attribute is no longer deprecated. The same is true of the value attribute for li elements, allowing you to specify the value for a specific list item. So to start a list at 4 and miss out 6 & 7, you would use:

<ol start="4">
   <li>Item 4</li>
   <li>Item 5</li>
   <li value="8">Item 8</li>
   <li>Item 9</li>

This gives:

  1. Item 4
  2. Item 5
  3. Item 8
  4. Item 9

The final ‘ō’ in Rogō

The final ‘ō’ in Rogō is an ‘o’ with a macron, which has numerical code 333 (&#333; for HTML) and HEX code 014D. This seems to cause some problems, as not all text editors are able to read/save the character, e.g. WinSCP’s internal editor, or are not, by default, set up with the correct encoding to read/save it, e.g. Eclipse. As a result, having edited files, we were finding that the titles of pages, for example, contained the ‘Å’ character instead.

We feel that it is perhaps unnecessary to use this special character, and it might be easier to just use a standard ‘o’ instead. However, in order to ensure the ‘ō’ is retained, it was necessary to take the following steps in the editors we use:

  • Eclipse (which gives a warning when trying to save a file that contains characters in cannot encode) – go to Window > Preferences > General >  Workspace and in the “Text file encoding” section, change the setting from the Default (Cp1252) to UTF-8.
  • WinSCP – rather than changing the encoding settings of the internal editor (which doesn’t seem to be possible), I changed the editor that is used to Notepad++, which has many other advantages over the internal editor.

However, there was still a problem with any ‘ō’ contained within the database, e.g. the contents of the help files. Initially, the database would not let me store the ‘ō’ character. This was fixed by changing the Collation from latin_swedish_ci (which it must have defaulted to) to utf8_unicode_ci. The ‘ō’ character can then be saved in the database, but the browsers I have tested it on (IE9, Firefox, Chrome) display the ‘ō’ as a question mark (only for ‘ō’s read from the database though, not ‘static’ ones in HTML files). The only way to get this to render properly in the pages is to replace the character with the html code &#333; or &#x14D;. Therefore, we could go through the SQL files for the help pages (in the install folder) and do a find/replace on all of the ‘ō’ characters, then replace the contents of the help tables.

However, this all seems a bit unnecessary just to get ‘ō’ rather than ‘o’, so we have suggested the on the Rogo mail list that we could drop the ‘ō’ when using it in text, and just use ‘o’.


A minor change to the assessment delivery page

For EMQs in Perception, we ‘manually’ (using our Question Maker) number the question stems with Roman numerals – (i), (ii) etc – and letter the answer options – A, B, C etc. However, in Rogo, the stems are automatically lettered by default. Therefore, having imported questions from Perception into Rogo, the stems had both letters and Roman numerals, e.g. A. (i) The first stem.

To fix this, the options were to change all of our questions when we imported them, or to remove the automatic stem lettering in Rogo. The former would be a prohibitively large amount of work, so thankfully the latter is merely a case of changing one CSS property in the paper/start.php file, line 370. The “list-style-type:upper-alpha” property of “.extmatch li” was changed to “list-style-type:none” to remove the item-marker. There are many possible values for this property – see