Question

2. What is the sample size, n, for a 95% confidence interval on the mean, if we know that the process’ standard error is 3.2 units, and we want to allow at most 1.0 units for our error?

3. Let’s say that you just randomly pulled 32 widgets from your production line and you determined that you need a sample size of 46 widgets, However, you get delayed in being able to pull another bunch of widgets from the line until the start of the next day. How many widgets should you now pull for your analysis?

4. What is the sample size, n, for a 98% confidence interval on the mean, if we know that the process’ standard error is 3.2 units, and we want to allow at most 0.5 units for our error?

5. What is the sample size, n, for a 95% confidence interval on the mean, if we know that the process’ standard error is 3.2 units, and we want to allow at most 0.5 units for our error?

Answer 1

2)

for 95 % CI value of z=	1.960
standard deviation σ=	3.2
margin of error E =	1
required sample size n=(zσ/E)2                                         =	40.0

3)

46  widgets ;as it will remain same to avoid bias

4)

for 98 % CI value of z=	2.33
standard deviation σ=	3.2
margin of error E =	0.5
required sample size n=(zσ/E)2                                         =	223.0

( try 222 if this comes wrong)

5)

for 95 % CI value of z=	1.96
standard deviation σ=	3.2
margin of error E =	0.5
required sample size n=(zσ/E)2                                         =	158.0