Sample Table of Specifications for Multiple Choice Exams

Sample Table of Specifications for Multiple Choice Exams in Medical School

To prepare a multiple choice exam or test you have to know the percentages of the topics depending on their importance to the subject and the hours spent in their discussion.

Let’s say you are preparing an exam for the prelim period, for your subject in Human Physiology in medical school; here are steps you can adapt.

1.       Assign the percentage per topic based on the course requirement:

Intro to human physiology – 10%The human body- 15%The muscular system -25%The skeletal system -25%The cardiovascular system -25%TOTAL = 100%

N.B. You can adjust the percentages according to your syllabus or academic requirements.

2.       Decide on how many items the test should be. Let’s say you have decided that the items for your Prelim exam are 150. The time allotted should at least be 2 hours for this exam, if 1 minute per question and 3 minutes per problem is assigned.

3.       Present your data in a table of specifications for clarity.

TOPIC NO. OF ITEMS

PERCENTAGE

Intro to Physiology

10

The Human Body

15

The Muscular System

25

The Skeletal System

25

The Cardiovascular system

25

TOTAL 100%

4.       Solve for the number of items of each topic by multiplying the percentage-decimal equivalent with the total number of items.

Intro to Physiology = 0.10 (10%) X 150 = 15 itemsThe Human Body = 0.15 (15%) X 150 = 22.50 itemsThe Muscular System = 0.25 (25%) X 150 = 37.50 itemsThe Skeletal System = 0.25 (25%) X 150 =37.50 itemsThe Cardiovascular System = 0.25 (25%) X 150 = 37.50 items

For a total of 150 items. Since there are no 0.5 questions, you may decide to which topic you would assign the 1 item excess.

Let’s say you have the final items assigned:

Intro to Physiology = 0.10 X 150 = 15 itemsThe Human Body = 0.15 X 150 = 23 itemsThe Muscular System = 0.25 X 150 = 37 itemsThe Skeletal System = 0.25 X 150 =37 itemsThe Cardiovascular System = 0.25 X 150 = 38 items

You come up with this table

TOPIC NO. OF ITEMS

PERCENTAGE

Intro to Physiology

15 10

The Human Body

23 15

The Muscular System

37 25

The Skeletal System

37 25

The Cardiovascular system

38 25

TOTAL 150 100%

5.       This is the simplest form of preparing for a table of specifications. You may want to be more specific and prepare a more detailed table assigning easy, average and difficult questions. The average questions should at least be 80% of your exams, while the easy at least 20% and the difficult, at least 15 %. This is recommended but the final decision still relies on the subject per se, and the learning ability of your students.

TOPIC Easy qsns.

Average qsns.

Difficult qsns.

NO. OF ITEMS

PERCENTAGE

Intro to Physiology

3 10 2 15 10

The Human Body

4 16 3 23 15

The Muscular System

5 28 4 37 25

The Skeletal System

5 28 4 37 25

The Cardiovascular system

5 28 4 38 25

TOTAL 22 111 17 150 100%

6.       You should be able to determine which questions are easy, average and difficult based on an item analysis that you have done in previous exams. This is an analysis of what questions were answered easily and correctly and which ones were difficult for the students. There are available software for item analysis that maybe available from your school or you could prepare one yourself through the semesters that you teach the subject.Another Sample Table of Specifications

Clinical Chemistry 1 subject – Prelim Exams

Topic Identification Multiple Choice

Problem Solving

Number of Items

Percentage

Intro to Clinical Chemistry

2 10 0 12 10

Laboratory Mathematics

2 14 20 36 30

Carbohydrates 3 33 0 36 30Lipids 3 33 0 36 30Total No. of Items

10 90 20 120 100%

DECIDE THE NUMBER OF ITEMS FOR YOUR EXAM, BASED ON THE HOURS AVAILABLE.

1.       You assign the percentage according to the importance of the topic to your subject, or you can also refer to the required weight of the topic by your school or accrediting institution.

2.                 Decide on the total number of items for the exam depending on the number of hours

assigned.3.                 At least 1 minute is given for easy questions and 3-5 minutes for difficult questions.

In case analyses, you may want to increase the time.4.    

             Based on your total items, you now get the number of items for each topic simply by multiplying the total score with the percentage. Below is the computation for this Table of Specifications.

How to solve the number of items for your Table of Specifications.

Introduction to clinical chemistry = 120 X 0.10 (10%) = 12 itemsLaboratory Mathematics = 120 X 0.30 = 36 itemsCarbohydrates = 120 X 0.30 = 36 itemsLipids = 120 X 0.30 =36 items

Total number of items = 120

Assign now the specific type of test for the items. As the instructor, you would know what type of test could effectively test the knowledge of your students with the different topics. Your Table of Specifications should reflect which topics are vital to your course.

1.            In this example, the Introduction to Clinical Chemistry would not use problem solving

but only multiple choice and identification. You can compose 10 items for multiple choice and 2 items for identification.

  What is a Weighted Mean?

A weighted mean is a kind of average. Instead of each data point contributing equally to the final mean, some data points contribute more “weight” than others. If all the weights are equal, then the weighted mean equals the arithmetic mean (the regular “average” you’re used to). Weighted means are very common in statistics, especially when studying populations.

The Arithmetic Mean.

When you find a mean for a set of numbers, all the numbers carry an equal weight. For example, if you want to find the arithmetic mean of 1, 3, 5, 7, and 10:

Add up your data points: 1 + 3 + 5 + 7 + 10 = 26.Divide by the number of items in the set: 26 / 5 = 5.2.What do we mean by “equal weight”? You can think of each number in the sum above to

contribute 1/5 to the total mean (as there are 5 numbers in the set).

The Weighted Mean.

In some cases, you might want a number to have more weight. In that case, you’ll want to find the weighted mean. To find the weighted mean:

Multiply the numbers in your data set by the weights.Add the numbers up.For that set of number above with equal weights (1/5 for each number), the math to find the

weighted mean would be:

1(*1/5) + 3(*1/5) + 5(*1/5) + 7(*1/5) + 10(*1/5) = 5.2.

Sample problem: You take three 100-point exams in your statistics class and score 80, 80 and 85. The last exam is much easier than the first two, so your professor has given it less weight. The weights for the three exams are:

Exam 1: 40 % of your grade. (Note: 40% as a decimal is .4.)Exam 2: 40 % of your grade.Exam 3: 20 % of your grade.What is your final weighted average for the class?

Multiply the numbers in your data set by the weights:.4(80) = 32.4(80) = 32.2(85) = 19Add the numbers up. 32 + 32 + 19 = 83.Weighted Mean Formula

The weighted mean is relatively easy to find. But in some cases the weights might not add up to 1. In those cases, you’ll need to use the weighted mean formula. The only difference between the formula and the steps above is that you divide by the sum of all the weights.

The image above is the technical formula for the weighted mean. In simple terms, the formula can be written as:Weighted mean = Σwx/ΣwΣ = the sum of (in other words…add them up!).w = the weights.x = the value.

To use the formula:

Multiply the numbers in your data set by the weights.Add the numbers in Step 1 up. Set this number aside for a moment.Add up all of the weights.Divide the numbers you found in Step 2 by the number you found in Step 3.In the sample grades problem above, all of the weights add up to 1 (.4 + .4 + .2) so you would divide your answer (83) by 1:83 / 1 = 83.However, let’s say your weighted means added up to 1.2 instead of 1. You’d divide 83 by 1.2 to get:83 / .8 = 69.17.Warning: The weighted mean can be easily influenced by outliers in your data. If you have very high or very low values in your data set, the weighted mean may not be a good statistic to rely on.Weighted Mean: Formula: How to Find Weighted Mean was last modified: July 27th, 2015 by Andale