Notes from Week 9, Wed 25th lecture on the group projects.

II. Participation points

For the group projects: Instead of turning in appendix with participants with final report, please out list of participants with full name and group number and give to us Monday or Tuesday next week.

** Participant form in folders -- one for each project team. **

III. Dealing with the data from group project


Visual: Distribution of scores

Numerical: central tendency & variability

Reliability: Subjective scoring


Validity: Are you measuring what you intended to measure?

Visual: Distribution of scores

Create graph either (a) by hand or (b) with a program like Powerpoint or Excel (only if you already know how to use -- by hand is just fine as long as it's neat)

X-axis: Numerical value of scores

Y-axis: Number of people who got each score (or range of scores)

Label graph so it's easy to read.

If you group scores on X-axis (i.e., 1-3, 4-6, 7-9), use 6-10 intervals, all equal.

Good test should yield a roughly normal-looking distribution (bell shape), since intelligence/ ability (what you are trying to measure) is distributed this way

If test too hard, scores will clump at bottom; if too easy, will clump at top.

Note: Different types of graphs might be appropriate depending on your data. If you measured two different abilities, two separate graphs may be more appropriate (check to see if distributions look different). If you have sorted people into categories (visual thinker vs verbal thinker), then you won't have scores on X-axis, you'll have the categories. Y-axis, again, will be the frequency (number) of people in the category.

Numerical: central tendency & variability

Central tendency: Mean, median, mode

Mean: add and divide by N --- ALL scores count

Median: find the middle score (or division point where half are above and half below)

Mode: look for the most frequent score

Symmetric distribution: Just give mean. If seriously skewed (bunched up at top or bottom) also give mode OR median.

Note: If your test is classifying people into CATEGORIES (i.e., autocratic leader vs. democratic leader) you won't be able to use the mean -- mode is the only one of the three that applies.

Variability: Range or standard deviation

Range: Max - min + 1

Example: 1 2 5 8 9 [9-1+1 = 9]

Standard deviation:

**Use only if you know what it means and how to calculate.** Basically, the standard deviation is the average distance of a score from mean

Reliability: Subjective scoring

Multiple judges: If you had subjective scoring (open-ended question, diagram or drawing), you should both score the results. Report how well you agreed on the scores -- within one point? Two points? Don't panic if agreement is poor -- just report this. Use the average of the two judges scores as the person's score.

Multiple types of questions:

If you had two different types of questions, or measured two aspects of an ability, calculate subscores for the different sections. Did people who scored high on one section tend to score high on the other section? This is what you'd expect.

Validity: Are you measuring what you intended to measure?

Face validity: Item has obvious connection to what you are measuring. Look at participant comments for items they thought were strange or irrelevant.

Construct validity: Test actually measures what you think it does (and not ability to follow instructions, or emotional ability if you are trying to measure visual, etc.)

Item analysis:

Divide people into top half and bottom half by their scores. Now look at how these two groups did on each item.

Are there any questions that the bottom half did better on than the top half? If so, this might be a bad item. Look at it carefully.


If people didn't answer some of the questions, you can (a) exclude them from the results

If you have lots of missing data, an alternative is to (b) just calculate total score using the items that everyone answered.

Note what you did in your results section.

NOTE: Not all of these procedures will be appropriate -- it depends on the kind of data you collected and what you are illustrating with the graphs. Some people may report multiple means; some only one. What matters is that your visual and numerical elements summarize your data in a way that is easy for the reader to understand and appropriate for your data.