An investment analyst has data for the past 8 years on each of two mutual funds, with the annual
rates of return for each listed in file XR11074. On average, each fund has had an excellent annual
rate of return over the time period for his data, but the a
Three years after receiving their degrees, graduates of a universitys MBA program have reported
their annual salary rates, with a portion of the data listed in file XR11097. Graduates in one of
the groups represented in the data are employed by consulting
CHAPTER
7
Statistical Inference
ESTIMATING A POPULATION MEAN
LEARNING OBJECTIVES
After completing the chapter, you should be able to
1. Define statistical inference and give the main reasons for sampling.
2. Describe the various sample selection procedure
Compare Means
Descriptive Statistics
VAR
Sample1
Sample2
Sample size
9
10
Mean
151.92222
137.99
t-test assuming equal variances (homoscedastic)
Degrees of Freedom
17
Hypothesized Mean Difference
0
Pooled Variance
317.26733
1.70236
Test Statistics
Two-tail
Compare Means
Descriptive Statistics
VAR
usatoday
washpost
Sample size
50
50
Mean
t-test assuming unequal variances (heteroscedastic)
Degrees of Freedom
73
Hypothesized Mean Difference
0
Pooled Variance
13.43653
1.63685
Test Statistics
Two-tailed distribu
Compare Means
Descriptive Statistics
VAR
Rolled
Regulation
Sample size
105
105
Mean
91.57143
89.57143
t-test assuming equal variances (homoscedastic)
Degrees of Freedom
208
Hypothesized Mean Difference
0
Pooled Variance
59.46841
1.87917
Test Statistics
Tw
Compare Means
Descriptive Statistics
VAR
ComputerA
ComputerB
Sample size
45
40
Mean
3,049.04444
3,122.55
t-test assuming unequal variances (heteroscedastic)
Degrees of Freedom
76
Hypothesized Mean Difference
0
Pooled Variance
37,922.76881
1.77909
Test Sta
S
Descriptive Statistics
VAR
Before
After
Sample size
5
5
Mean
0.37
0.462
Paired two-sample t-test
Degrees of Freedom
Hypothesized Mean Difference
Pooled Variance
Test Statistics
Pearson Correlation Coefficient
4
0
0.00196
6.14701
0.7844
Two-tailed distri
P. 273# 40, 42
P. 272# 38
P. 271# 28
I. It has been reported that households in the West spend an annual average of $6050 for groceries.
Assume a normal distribution with a standard deviation of $1500. Source: David Stuckey and Sam Ward,
Home Cooked,