Question

Student Number	Credit Hours
1	4
2	11
3	3
4	5
5	7
6	11
7	10
8	8
9	12
10	12
11	6
12	6
13	12
14	7
15	8
16	5
17	6
18	7
19	10
20	11
21	12
22	8
23	6
24	10
25	11
26	3
27	5
28	12
29	8
30	11

Thirty graduate students were asked how many credit hours they were taking in the current quarter.

Calculate the mean, median, standard deviation, variance, and range for this sample using Excel. Write a sentence explaining what each measure means.

1. What is the standard error of the mean based on the data?
2. What would be the best point estimate for the population credit hours? (“Population” refers to all graduate students’ credit hours in the universe.)
3. What is the 95% confidence interval for the means of credit hours? What is the 90% confidence interval?

Answer 1

Firstly, put the data onto the excel:

Mean, Median, Standard Deviation, Variance, and Range

To calculate all these values, we need to find descriptive statistics using excel:

Select the data and get the results

Therefore, the values are:

Mean = 8.233 (It indicates the average credits hours of a student)

Median = 8 (It indicates the middle value of the data)

Standard Deviation =2.922 (It indicates the deviation of data points from the mean)

Variance = 8.529 (It indicates the variation in the data)

Range = 9 (It indicates the difference in maximum and minimum credit hours)

a. The standard error

The standard error value is given in the summary output

Standard error = 0.5332

b. The best point of estimate would be the mean value

c. confidence interval

Following formula can be used to calculate the confidence interval:

95% confidence interval:

The value of z at a 95% confidence interval is 1.96

The 95% confidence interval is (7.188, 9.278)

90% confidence interval:

The value of z at a 90% confidence interval is 1.64

The 90% confidence interval is (7.358, 9.1074)