Asked Nov 22, 2019

You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately σ=37.8σ=37.8. You would like to be 90% confident that your estimate is within 1 of the true population mean. How large of a sample size is required?


Expert Answer

Step 1

Step-by-step procedure to obtain the value of z using MINITAB:

  • Choose Graph > Probability Distribution Plot choose View Probability > OK.
  • From Distribution, choose ‘Normal’ distribution.
  • Click the Shaded Area
  • Choose Probability and Both Tail for the region of the curve to shade.
  • Enter the Probability value as 10.
  • Click OK.

Output using the MINITAB software is given below:


Image Transcriptionclose

Distribution Plot Normal, Mean=0, StDev=1 0.4 0.3 0.2 0.1 0.05 0.05 0.0 -1.645 1.645 X Density

Step 2

From the output, the value of z is 1.645 for 90% confidence...


Image Transcriptionclose

ZO п- E 1.645 (37.8) -3,866.5 3,867


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