Respuesta :
Answer:
A 95% prediction interval for the drying time for the next trial of the paint is between 3.25 and 4.33 hours.
Step-by-step explanation:
First we have to find the sample mean and the sample standard deviation.
We have 15 measurements. Using a calculator, the mean is [tex]\overline{x} = 3.79[/tex] and the standard deviation is of [tex]s = 0.97[/tex].
Now, we have the standard deviation for the sample, which means that the t-distribution is used to solve this question.
T interval
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 15 - 1 = 14
95% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 14 degrees of freedom(y-axis) and a confidence level of [tex]1 - \frac{1 - 0.95}{2} = 0.975[/tex]. So we have T = 2.1448
The margin of error is:
[tex]M = T\frac{s}{\sqrt{n}} = 2.1448\frac{0.97}{\sqrt{15}} = 0.54[/tex]
In which s is the standard deviation of the sample and n is the size of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 3.79 - 0.54 = 3.25 hours
The upper end of the interval is the sample mean added to M. So it is 3.79 + 0.54 = 4.33 hours
A 95% prediction interval for the drying time for the next trial of the paint is between 3.25 and 4.33 hours.
