Question

I took a sample of the grade point averages for students in my class. For the 25 students, the standard deviation of grade points was 0.65 and the mean was 2.89. A 95% confidence interval for the average grade point average for all students in my class is __________?

Answer 1

Answer: = ( 2.64, 3.14)

Therefore at 95% confidence interval (a,b) = ( 2.64, 3.14)

Explanation:

Confidence interval can be defined as a range of values so defined that there is a specified probability that the value of a parameter lies within it.

The confidence interval of a statistical data can be written as.

x+/-zr/√n

Given that;

Mean x = 2.89

Standard deviation r = 0.65

Number of samples n = 25

Confidence interval = 95%

z(at 95% confidence) = 1.96

Substituting the values we have;

2.89+/-1.96(0.65/√25)

2.89+/-1.96(0.13)

2.89+/-0.25

= ( 2.64, 3.14)

Therefore at 95% confidence interval (a,b) = ( 2.64, 3.14)