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Statistics and Probability

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Moderate

Degrees of Freedom for Two Population Means

STATS-GLPG0R

A researcher is interested in testing to determine if the mean of population one is greater than the mean of population two. He randomly selects a sample of $9$ items from population one resulting in a mean of $14.3$ and a standard deviation of $3.4$.

Then he randomly selects a sample of $14$ from population two resulting in a mean of $11.8$ and a standard deviation of $2.9$.

Assuming that the populations are normally distributed with equal standard deviation, what are the degrees of freedom for this test?

A

$23$

B

$22$

C

$21$

D

$2$