Question

The grade point averages​ (GPA) for 12 randomly selected college students are shown on the right. Complete parts​ (a) through​ (c) below. Assume the population is normally distributed.

2.2 3.4 2.9 1.8 0.8 4.0 2.4 1.3 3.9 0.5 2.4 3.3 ​

(a) Find the sample mean.

x = _____ ​(Round to two decimal places as​ needed.) ​

(b) Find the sample standard deviation.

s= ______ (Round to two decimal places as​ needed.)

​(c) Construct a 95​% confidence interval for the population mean mu.

A 95​% confidence interval for the population mean is( ____, ____ ) . ​(Round to two decimal places as​ needed.)

Answer 1

A
Mean
	2.2
	3.4
	2.9
	1.8
	0.8
	4
	2.4
	1.3
	3.9
	0.5
	2.4
	3.3
Sum	28.9
Count	12
Mean	2.41
B
Standard Deviation
	Nos	Square of difference from mean
	2.2	0.04
	3.4	0.98
	2.9	0.24
	1.8	0.37
	0.8	2.59
	4	2.53
	2.4	0.00
	1.3	1.23
	3.9	2.23
	0.5	3.64
	2.4	0.00
	3.3	0.80
	28.9	14.65
SD		square root of (14.65/12)
	SD	1.10
Confidence Level at 95%
Step 1	Degree of Freedom	12-1=11
Step 2	(1-.95)/2=.025= alpha
Step 3 As per t distribution table		2.201
Step 4	0.32
At 95% confidence mean is =
	2.201*.32	0.70