A wildlife biologist wants to determine the mean weight of adult red squirrels. She captures 10
Squirrels she believes to be representative of the species and weighs them, finding a mean of 12.32
Grams and standard deviation of 1.88 gm. Assuming these squirrels can be considered a random
Sample of all red squirrels which of the following formulas gives a 95% confidence interval for the
Mean weight of all squirrels?
A) $12.32 \pm 1.96 ( 1.88 / \sqrt { 10 } )$
B) $12.32 \pm 2.262 ( 1.88 / \sqrt { 10 } )$
C) $12.32 \pm 2.228 ( 1.88 / \sqrt { 10 } )$
D) $12.32 \pm 2.268 ( 1.88 / \sqrt { 9 } )$
E) $12.32 \pm 2.228 ( 1.88 / \sqrt { 9 } )$

Question

A wildlife biologist wants to determine the mean weight of adult red squirrels. She captures 10
Squirrels she believes to be representative of the species and weighs them, finding a mean of 12.32
Grams and standard deviation of 1.88 gm. Assuming these squirrels can be considered a random
Sample of all red squirrels which of the following formulas gives a 95% confidence interval for the
Mean weight of all squirrels? 
A) $12.32 \pm 1.96 ( 1.88 / \sqrt { 10 } )$
B) $12.32 \pm 2.262 ( 1.88 / \sqrt { 10 } )$
C) $12.32 \pm 2.228 ( 1.88 / \sqrt { 10 } )$
D) $12.32 \pm 2.268 ( 1.88 / \sqrt { 9 } )$
E) $12.32 \pm 2.228 ( 1.88 / \sqrt { 9 } )$

Quizplus · Accepted Answer

For a small sample size (n < 30), the t-distribution is used. With 9 degrees of freedom (n-1), the t-value for a 95% confidence interval is approximately 2.262.

A Wildlife Biologist Wants to Determine the Mean Weight of Adult