PSYC 201 - Dr. Pierce
Lab: Variability and standard scores
1. For the following set of scoresfrom a sample, please
a). Calculate the mean, median,sum of squares, the variance, and the
standard deviation. Please show all of your work. Make sure you label the variance and the
standard deviation with the appropriate symbol.
b). Use SPSS to check your work.
c). Convert each raw score to a standard score.
X
--
8
9
12
15
16
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2. For the following set of scores from a population, please
a). Calculate the mean, median,sum of squares, the variance, and the
standard deviation. Please show all of your work. Make sure you label the variance and the
standard deviation with the appropriate symbol.
b). Convert each raw score to a standard score
X
--
15
18
21
22
26
28
---
3. For the following set of scores from a sample, please
a). Calculate the mean, median, sum of squares, the variance, and the
standard deviation. Please show all of your work. Make sure you label the variance and the
standard deviation with the appropriate symbol.
b). Use SPSS to check your work.
X
----
10.2
15.3
6.8
27.4
22.7
7.9
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4. For the following set of scores from a population, please
a). Calculate the mean, median, sum of squares, the variance, and the
standard deviation. Please show all of your work. Make sure you label the variance and the
standard deviation with the appropriate symbol.
X
---
105
115
89
98
103
95
---
5. In the population the mean score for a measure of memory function is 17.3 and the standard deviation is 5.0. In the population the mean score for a test of vocabulary is 58 and the standard deviation is 10. A person has a score of 20.3 on the measure of memory function and a score of 63 on the test of vocabulary. Is the person stronger in terms of their memory or their vocabulary? Why do you think so?
6. The standard deviation of a set of IQ scores is 15. What does this number tell you about the scores in the set?
7. Why can’t you use the sum of squares to compare the variability of scores for a group of 10 people to the variability of scores for a group of 20 people?
8. Why shouldn’t the range be used as the only measure of variability?
9. Why is the standard deviation more easy to interpret than the variance?
10. What is the “unit of measurement” for a standard score (Z-score)?
11. What are the advantages of converting raw scores to standard scores?
PSYC 201 - Dr. Pierce
Lab: Normal curve, percentile scores
Please show all of your work for each of the following questions.
1. Draw the normal curve and, on the x-axis, label the standard scores ranging from -3 to +3 (you only need to use whole numbers). Please write in the percentile score for each standard score (i.e., -3, -2) just below that standard score.
2. Find the percentile scores that correspond to each of the following standard scores: +1.6, -1.6, 0.0, +2.9, -.53
When answering the questions below, it will be helpful to start by drawing a graph of the normal curve.
3. For a normally distributed set of raw scores, what percentage of scores fall between a z-score of -1.62 and +2.30?
4. For a normally distributed set of raw scores, what percentage of raw scores fall between a z-score of +0.83 and a z-score of +2.15?
5. For a normally distributed set of raw scores, what percentage of raw scores fall between a z-score of -.65 and a z-score of -.87?
6. A psychologist is using a questionnaire measure of depression to help in diagnosing clients with depression. The manual for the questionnaire indicates that clients who score in the top 5% on the questionnaire fall in the "clinically depressed" range. The mean of all of the scores on the questionnaire is 22 and the standard deviation of scores on the questionnaire is 5. What is the highest raw score that a client could get on the questionnaire and still not be considered to be clinically depressed?
7. The top 2% of students in a math class are selected to go into an accelerated math class. The mean grade is 85 and the standard deviation is 5. What s the lowest grade a person could receive and still get into the accelerated math class?