Question

The average wall thickness of 25 panes of glass is 4.05 mm. The standard deviation of the thickness of the 25 panes is measured to be 0.08 mm. What is the 90% confidence interval of the mean of wall thickness

Answer 1

Answer:

u => 4,028

Step-by-step explanation:

To find the answer, we have the following formula:

u => m - t (alpha, n-1) * [sd / (n) ^ (1/2)]

where m is the mean.

where sd is the standard deviation.

where n is the sample size.

t is a parameter that depends on the confidence interval and the sample size.

alpha = 1 - ci

ci = 90% = 0.9

Therefore, alpha = 1 - 0.9 = 0.1.

n - 1 = 25 - 1 = 24

So it would come being t (0.1, 24), if we look in the table, which I will attach the value of t is equal to 1.318.

We know the rest of the values, m = 4.05; sd = 0.08; n = 25

u => 4.05 - 1,318 * [0.08 / (25) ^ (1/2)]

u => 4.028

Which means that the interval with a 90% confidence of the wall thickness measurement is:

u => 4.028