The document provides descriptive statistics for hours studied for an exam by 40 students. It includes a tally table showing the hours studied and frequency, as well as calculations for the total hours studied, mean, median, and mode. The mean was 5.6 hours. The median was the middle number of the data arranged in ascending order. The mode was the number that appeared most often in the tally table, which was 6 hours studied. A second table shows sample grades for a quiz and asks to calculate the mean, median, and mode, and draw a histogram to determine if the data is normally, negatively, or positively skewed.

1. Descriptive Statistics for Psychology

2. Hours Studied Tally Frequency Total Hours
Studied
10 I 1 10
9 III 3 27
8 IIII 4 32
7 IIII 5 35
6 IIII III 8 48
5 IIII II 7 35
4 IIII 5 20
3 IIII 4 12
2 II 2 4
1 I 1 1
0 0
N=40 ∑ = 224
Total hours studied = Hours studied X frequency

3. The mean, the arithmetic average of all
scores under consideration, is computed
by dividing the sum of the scores by the
number of scores.
224 = 5.6 = mean number of hours studied for the exam
40

4. The median is the point at which 50% of
the observations fall below and 50% above
or, in other words, the middle number of a 10
set of numbers arranged in ascending or 9
descending order.
8
7
6
5
4
3
2
1
0

5. The mode is the number that appears most often
Hours Studied Frequency
10 1
What is the Mode 9 3
according to this table?
8 4
7 5
6 8
5 7
4 5
3 4
2 2
1 1
0 0

6. Histogram

8. negative positive

9. Now it’s your turn!
Descriptive Statistics Activity
Below is a random sample of grades from a recent quiz.
90, 60, 65, 70, 85, 95, 50, 80, 70, 60, 50, 65, 75, 80, 85, 70, 65, 55, 100, 65, 70, 85,
80, 65, 75
1. Calculate the Mean, median, and mode.
a. Create a histogram.
b. Is the data normal, negatively, or positively skewed?

10. Tally Score Frequency total
I 100 1 100
I 95 1 95
I 90 1 90
III 85 3 255
III 80 3 240
II 75 2 150
IIII 70 4 280
IIIII 65 5 325
II 60 2 120
I 55 1 55
II 50 2 100

11. MEDIAN? MODE?
100 100
95 95
90 90
85 85
85 85
85 85
80 80
80 80
80 80
75 75
75 75
70 70
70 <- 70
70 70
70 70
65 65
65 65
65 65
65 65
65 65
60 60
60 60
55 55
50 50
50 50