A biologist investigates whether the wing lengths of house f

A biologist investigates whether the wing lengths of house flies have changed. In 1970, before air pollution control measures went into effect, the wing size was on average 45 x .1 mm. In 2000, a new study has been made and the data are:Length(.1 mm)

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. Has the wing size changed? Use a p-value approach to the t-test at the = 10% significance level. H0: =45 (2-tailed).

Solution

H0: mu = wing size = 45

Ha: mu not equal to 45

Two tailed test

n = sample size = 50

alpha = 0.1

df = 99

We first find out the sample mean, std error as above

Mean difference = 0.5

t statistic = 1.276

The P-Value is .204941.

The result is not significant at p < .10.

Hence it is statistically evident that wing size has not changed at 10% sign level for 2 tailed