In: Statistics and Probability
An SRS produced the following data. Is browser choice and grade level independent? The responses were categorized below. Test at the .05 significance level. (α = .05)
Safari |
Firefox |
Chrome |
|
Freshmen |
20 |
25 |
40 |
Sophomore |
40 |
30 |
30 |
Junior |
50 |
25 |
50 |
Senior |
90 |
20 |
75 |
What is your conclusion in plain English?
a) There is not enough evidence to suggest that browser choice and grade level are dependent.
b) Evidence suggests that browser choice and grade level are independent.
c) There is not enough evidence to suggest that browser choice and grade level are independent.
d) Evidence suggests that browser choice and grade level are dependent.
ANSWER::
Expected frequency of a cell = sum of row*sum of column / total sum | |||||||
Expected Frequencies | |||||||
Total | |||||||
200*85/495=34.343 | 100*85/495=17.172 | 195*85/495=33.485 | 85 | ||||
200*100/495=40.404 | 100*100/495=20.202 | 195*100/495=39.394 | 100 | ||||
200*125/495=50.505 | 100*125/495=25.253 | 195*125/495=49.242 | 125 | ||||
200*185/495=74.747 | 100*185/495=37.374 | 195*185/495=72.879 | 185 |
(fo-fe)^2/fe | ||||||
5.990 | 3.569 | 1.268 | ||||
0.004 | 4.752 | 2.240 | ||||
0.0051 | 0.0025 | 0.0117 | ||||
3.1123 | 8.0764 | 0.0617 |
Chi-Square Test Statistic,χ² = Σ(fo-fe)^2/fe =
29.093
Level of Significance = 0.05
Number of Rows = 4
Number of Columns = 3
Degrees of Freedom=(#row - 1)(#column -1) = (4- 1 ) * ( 3- 1 )
= 6
p-Value = 0.0001 [Excel function:
=CHISQ.DIST.RT(χ²,df) ]
Decision: p-value < α , Reject Ho
Option:: (d) is correct...........
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