SOLUTION: A child psychologist wants to estimate the mean age at which a child learns to talk using a confidence interval. Find the sample size necessary for a 99% confidence interval with m

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Question 1174137: A child psychologist wants to estimate the mean age at which a child learns to talk using a confidence interval. Find the sample size necessary for a 99% confidence interval with maximum error estimate of 4 weeks for the mean age at which a child learns to talk. Assume σ = 25 weeks.
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 
Hi,

Normal Distribution:  σ = 25 and ME = 4 
Find the sample size necessary for a 99% confidence interval 

 ME =%28+z%2Asigma%2Fsqrt%28n%29%29
Or
  n =  +%28%28z%2Asigma%29%2FME%29%5E2

  n = +%28%282.576%2A25%29%2F4%29%5E2 = 16.1  0r  17 rounded up (to be on the safe side)

   17 the sample size necessary for a 99% confidence interval 

 = CI	z = value
90%	z =1.645
92%	z = 1.751
95%	z = 1.96
98%	z = 2.326
99%	z = 2.576

Wish You the Best in your Studies.