I would like to invite you to be the keynote speaker for the upcoming IMIA Congress to be held in April in Washington DC, theme: United we are stronger.

We are not in a position to pay but we have 400-600 attendees annually and you presented for one of our smaller events in Oregon I believe and I really liked it that you had an overall overview of what a profession needs to evolve. If you are interested I’d love to tell you more about it. Just call me at 781 801 6898 or let me know how to get in touch with you. Info of event here:http://www.imiaweb.org/conferences/2015conference.asp

time frame for keynote 10-11am on Friday April 24, 2015.

Best,

Izabel Arocha

IMIA Executive Director

cell 781 801 6898

iarocha@imiaweb.org

I have a question about point biseral correlation. I want to measure the correlation between gender and frequency of attending church. I set male=1 and female=2 in SPSS and did the correlation analysis. The output showed negative value of the coefficient. Should I interpret the result as female has lower frequency and male have higher frequency. Also as the percentage of male and female are 28% and 72% respectively, will this uneven distribution affects the calculation of coefficient.

]]>I know it’s been a while since you posted this piece but I’ve come across a similar problem myself and was wondering whether you could help me?

I’m looking at a 330 item test which had a KR-20 score of 0.722 – pretty low. The point biserials are pretty low across the board (but that’s an issue across the bank of questions) but there are a lot of questions with high p-values and the range of total scores is quite narrow.

I was wondering how you came to the conclusion that a question is adding nothing to the assessment – is this based on the p-values? Also how are you applying the standard deviation to the question data (p-values again?) to define whether questions provided ‘measurement information’?

Thanks,

Neil

]]>Regards,

]]>Patterns of relations can also change when test content is confounded with difficulty [e.g., (A) solving a one variable algebraic expression early in the test versus (B) reading and understanding a word problem, formulating a one variable mathematical expression from text and then solving the one variable algebraic expression later in the test]. Difficulty is confounded with content. Moreover, one can easily argue that the math test is multidimensional, involving verbal ability, analytical reasoning, and mathematical ability. In this case, the latter item can be broken down into three factors that combine into a linear composite when one score is reported. The early question only loads on one component in the composite and results in a lower point biserial. To the extent that verbal, analytical, and math are positively related in the latter question, then a higher point biserial correlation results because there are three positively related components producing the higher correlation. I hope this helps.

]]>I like your MMblog for the fine contents.

I have one query about one interesting findings we got.

We categorized 1115 A-type MCQs in three groups depending on their difficulty level (high, medium and low). The effect of item difficulty was analyzed vis-a-vis various discrimination indices (discrimination index, DI; point biserial correlation, RBP; corrected RPB; biserial correlation, RBIS and corrected RBIS). The correlation was determined between item difficulty and discrimination indices.

The item difficulty significantly influenced all discrimination indices (p <0.001). The items with higher difficulty had significantly lower degree of discriminating power. The item difficulty-discrimination index plot showed inverted U shape relationship. The RPB showed significant polynomial with item difficulty (p <0.001). However, the RBIS showed significant linear relationships with item difficulty (p <0.001).

My conclusion is that Items in low difficulty range ( more than 0.7) are best at differentiating the high and low achievers as revealed by item-total correlation indices.

Any reaction ?

Also please tell what could be an explanation (This is contrary to belief that that difficult item are good for discrimination).

—

Dr. KK Deepak MD, PhD, MNAMS

Professor of Physiology,

Medical Education Unit,

Item Bank Administrator ( IDEAL Consortium ) College of Medicine,

University of Dammam, Dammam

Kingdom of Saudi Arabia

( on assignment till Sept 2010 )

In terms of money, the said thing about it is that this certification exam is probably not free. Let’s assume that you are taking this exam in a testing center or even hiring a proctor and renting hotel conference space. If you are taking this exam in a testing center and the negotiated contract between the test center and the test sponsor or certifying agency is negotiated on an hourly rate, guess how much money is lost? As a very conservative estimate, the rate for the test center is $10 per testing hour per person. I personally know of rates that far exceed this value but it’s very conservative and can demonstrate the point. Going back to our very conservative 1000 examinees per year who have wasted 125 person hours, we see that over $1000 dollars is gone. That’s only with 1000 examinees per year. Please don’t tell me the actual number of examinees per year; I think I might cry. You get my point though!

Once again, I’ve enjoyed your post. Keep up the good work!

Regards,

DB