Question

Specifications for a piece of material used in the manufacture of a bed mattress require that the piece be between a Lower and Upper value (in inches) centered around the process mean. The process that produces the piece yields a mean of 52 and a standard deviation of 0.7 inches. The distribution of output is normal. Within what values will 85.2 percent of sample means fall, if samples of n = 13 are taken and the process is in control?

Question 5 options:

51.353 , 52.646

50.987 , 53.012

51.719 , 52.28

50.255 , 53.744

None of the Above

Answer 1

Solution :

Given that,

Sample size = n = 13

Z/2 = Z0.074 = 1.447

Margin of error = E = Z/2* ( /n)

= 1.447 * ( 0.7/ 13)

Margin of error = E = 0.281

At 85.2% confidence interval estimate of the population mean is,

- E < < + E

52 - 0.281 < < 52 + 0.281

51.719 < < 52.281

(51.719 , 52.281), Option 3rd is correct