- #1
Fear_of_Math
- 7
- 0
Hello again,
I have a question here that asks me to find how large a sample size is, but I have no Standard deviation. How would you tackle this>
How large a sample size do we need to estimate the mean annual income of natives in New York, correct to within $1000 with probability 0.99? No information is available to us about the standard deviation of their annual income. We guess that nearly all of the incomes fall between $0 and $120,000 and that this distribution is approximately normal.
Here's what I see:
1 - alpha = 0.99 therefore alpha =0.01 /2 = 0.005
This gives a Z* of 2.575 (because it states normal distribution)
The 99% CI is (0, 120000).
I know that n = [Z*s/m]squared, buty I have neither s, nor m...
As always, the feedback and guidance is appreciated =)
I have a question here that asks me to find how large a sample size is, but I have no Standard deviation. How would you tackle this>
How large a sample size do we need to estimate the mean annual income of natives in New York, correct to within $1000 with probability 0.99? No information is available to us about the standard deviation of their annual income. We guess that nearly all of the incomes fall between $0 and $120,000 and that this distribution is approximately normal.
Here's what I see:
1 - alpha = 0.99 therefore alpha =0.01 /2 = 0.005
This gives a Z* of 2.575 (because it states normal distribution)
The 99% CI is (0, 120000).
I know that n = [Z*s/m]squared, buty I have neither s, nor m...
As always, the feedback and guidance is appreciated =)