Thirty-five items are randomly selected from a population of 370 items. The sample mean is 34, and the sample standard deviation 8. Develop a 90% confidence interval for the population mean.
It tells me to round every answer to 3 decimals, and to round the final answer to 2 decimals. I keep getting 33.31 to 34.96, and it tells me its wrong. Help please
Confidence interval: x - E < µ < x + E, where:
x = sample mean (34, in this case)
E (Margin of Error) = Zα/2 *
Zα/2 = Ƶ-critical score, based on 90% confidence level (1.645, in this case)
= Sample standard deviation (8, in this case)
n = sample amount (35, in this case)
x - E < µ < x + E then becomes:
< µ <
34 – 2.224 < µ < 34 + 2.224
31.776 < µ < 36.224