A manufacturer claims that the mean driving per mile of its sedans is less than that of its leading competitor. You conduct a study using 28 randomly selected sedans from the manufacturer and 32 from the leading competitor. The results are given below
Manufacturer |
Competitor |
---|---|
X1 = 0.48 /mi |
X2 = 0.5 /mi |
s1 = 0.05 /mi | s2 = 0.07 /mi |
n1 = 28 | n2 = 32 |
3. What is the pooled standard deviation?
4. Observed test statistic
5. The degrees of freedom for the test statistic
Tries 0/5 |
6. P-value:
Tries 0/5 |
3)
Pooled Std.dev
sp = sqrt((((n1 - 1)*s1^2 + (n2 - 1)*s2^2)/(n1 + n2 - 2))*(1/n1 +
1/n2))
sp = sqrt((((28 - 1)*0.05^2 + (32 - 1)*0.07^2)/(28 + 32 - 2))*(1/28
+ 1/32))
sp = 0.0159
4)
Test statistic,
t = (x1bar - x2bar)/sp
t = (0.48 - 0.5)/0.0159
t = -1.258
5)
df = n1 + n2 - 2 = 58
6)
P-value Approach
P-value = 0.1067
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