Answer :
The standard error of the sample mean is 1.21.
Given;
Suppose a diet regimen for men results in an average weight loss of between 13. 4 and 18. 3 pounds, according to a 95% confidence interval. These findings were based on a group of 42 men who were classified as overweight at the beginning of the four-month trial.
A 95% confidence interval for a population mean is (13.4, 18.3)
Upper limit = 18.3
Lower limit = 13.4
Since population SD is unknown, this interval is constructed using the t distribution.
n = 42
c = 0.95
∴ α = 1 - c = 1 - 0.95 = 0.05
α/2 = 0.025
Also, d.f = n - 1 = 42 - 1 = 41
∴ ta/2.d.f = ta/2.n-1 = t0.025,41 = 2.02 . . . . use t table
Now,
The margin of error = (Upper limit - Lower limit)/2
= (18.3 - 13.4)/2
= 2.45
But,
Margin of error = ta/2.d.f- * (s / \sqrt{} n)
Margin of error = ta/2.d.f- * Standard error
2.45 = 2.02 * Standard error
Standard error = 1.2129
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