Posted by Desire on Wednesday, November 25, 2009 at 12:02pm.
Assume we draw a simple random sample from a population having a mean of 100 and a standard deviation of 16. What is the probability that a sample mean will be within plusorminus two of the population mean for each of the following sample sizes?
n = 50
n=100
n=200
n=400

Stats  PsyDAG, Thursday, November 26, 2009 at 7:22am
The probability of being within Z = ±2 for a normal distribution always approximates 95%. However, what you might be seeking is the high and low values that cut off that proportion.
Standard error of the mean (SE) = standard deviation/square root of n
Z = (raw score  mean)/SE
±2 = (raw score  100)/SE
Use the four SEs to find the raw score (±).
I hope this helps.

Stats  Desire, Saturday, November 28, 2009 at 2:33am
I don't understand how to get the answer using the formula.

Stats  Desire, Monday, November 30, 2009 at 12:25pm
For n = 100:
Lower limit: 100  2*16/sqrt(100) = 96.8
Upper limit: 100 + 2*16/sqrt(100) = 103.2
I can't get the answer for the other ones

Stats  Desire, Tuesday, December 1, 2009 at 1:12pm
Can you please help me solve for N
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