David E. Brown is an expert in wildlife conservation. In his book The Wolf in th

Question

David E. Brown is an expert in wildlife conservation. In his book The Wolf in the Southwest: The Making of an Endangered Species (University of Arizona Press), he records the following weights of adult grey wolves from two regions in Old Mexico.

Chihuahua region: x1 variable in pounds

Durango region: x2 variable in pounds

(a) Use a calculator with mean and standard deviation keys to calculate x1, s1, x2, and s2. (Use 2 decimal places.)

x1= 75.8

s1=8.32

x2=66.83

s2=8.87

(b) Let 1 be the mean weight of the population of all grey wolves in the Chihuahua region. Let 2 be the mean weight of the population of all grey wolves in the Durango region. Find a 95% confidence interval for 1 – 2. (Use 2 decimal places.)

lower limit=

upper limit=

Explanation / Answer

PART A.

PART B.
CI = x1 - x2 ± Z a/2 * Sqrt ( sd1 ^2 / n1 + sd2 ^2 /n2 )
Where,
x1 = Mean of Sample 1, x2 = Mean of sample2
sd1 = SD of Sample 1, sd2 = SD of sample2
a = 1 - (Confidence Level/100)
Za/2 = Z-table value
CI = Confidence Interval
Mean(x1)=75.8
Standard deviation( sd1 )=8.32
Sample Size(n1)=10
Mean(x2)=66.83
Standard deviation( sd2 )=8.87
Sample Size(n12=18
CI = [ ( 75.8-66.83) ±Z a/2 * Sqrt( 69.2224/10+78.6769/18)]
= [ (8.97) ± Z a/2 * Sqrt( 11.2932) ]
= [ (8.97) ± 1.96 * Sqrt( 11.2932) ]
= [2.3834 , 15.5566]

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