Question

A procurement specialist has purchased 25 resistors from Vendor 1 and 35 resistors from Vendor 2. Each resistor’s resistance was measured and reported in Problem 4 spreadsheet of Homework 2.xlsx. You want to compare mean performance. Use R, and draw conclusions with 0.05 significance. a. First perform the appropriate test to determine whether to assume equal or unequal dispersions of resistance for the two vendors. b. Based on your answer in part a, compare mean performance of the vendors with the appropriate ? test.

Vendor 1
96.8
100
100.3
98.5
98.3
98.2
99.6
99.4
99.9
101.1
103.7
97.7
99.7
101.1
97.7
98.6
101.9
101
99.4
99.8
99.1
99.6
101.2
98.2
98.6

Vendor 2
108.8
106.8
102.7
104.7
110
100.2
103.2
103.7
106.8
105.1
104
106.2
102.6
99.3
99
108
104.3
110.8
104
106.3
102.2
102.8
104.2
103.4
104.6
102.5
106.3
110.2
107.2
105.4
106.4
106.8
102.1
106.1
110.7

Answer 1

While testing the variances of resistance for the two vendors,

The value of F statistic = 0.26

and P-value = 0.001035

Since P-value < 0.05, so at 5% level of significance we reject H₀ and we can conclude that two variances are not significantly different.

Assuming two variances are equal, testing the equality of means of resistance for the two vendors, one need to perform a two sample t test with equal variances.

The value of t statistic = -8.4067

and P-value = 0

Since P-value < 0.05, so at 5% level of significance we reject H₀ and we can conclude that two means are significantly different.