In: Statistics and Probability
In a sample of 28 cups of coffee at the local coffee shop, the temperatures were normally distributed with a mean of 182.5 degrees with a sample standard deviation of 14.1 degrees. What would be the 95% confidence interval for the temperature of your cup of coffee?
Solution :
Given that,
= 182.5
s = 14.1
n = 28
Degrees of freedom = df = n - 1 = 28 - 1 = 27
At 95% confidence level the t is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
t /2,df = t0.025,27 =2.052
Margin of error = E = t/2,df * (s /n)
= 2.052 * (14.1 / 28 )
= 5.5
Margin of error = 5.5
The 95% confidence interval estimate of the population mean is,
- E < < + E
182.5 - 5.5 < < 182.5 + 5.5
177 < < 188
The temperature of cup of coffee IS ( 177 , 188 )