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Question
NARRBEGIN: SA_108_112The following values have been calculated using the TDIST and TINV functions in Excel. These values come from a t- distribution with 15 degrees of freedom.
These values represent the probability to the right of the given positive values.
| Value | t -probability |
| 1.00 | 0.1666 |
| 1.20 | 0.1244 |
| 1.40 | 0.0909 |
| Probability | t -value |
| 0.20 | 1.3406 |
| 0.10 | 1.7531 |
| 0.05 | 2.1315 |
You are trying to estimate the average amount a family spends on food during a year. In the past the standard deviation of the amount a family has spent on food during a year has been approximately $800. If you want to be 95% sure that you estimated average family food expenditures within $50, how many families do you need to survey?
Answer
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