The number of cars in 25 families is shown in the table. Calculate the mean number of cars in a family.
1 answer:
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Answer:
1.91° and -1.91°.
Step-by-step explanation:
2.8% of the thermometers are rejected on either end of the curve. The bottom end, where the readings are too far below the mean, will have an area from this point to the left tail of the curve of 0.028.
The top end, where the readings are too far above the mean, will have an area from this point to the left tail of the curve of 1-0.028 = 0.972.
We look in a z table for these values. We look within the cells of the table; the closest value to 0.028 is 0.0281, which corresponds with a z score of -1.91. The closest value to 0.972 is 0.9719, which corresponds with a z score of 1.91.
We substitute these values into the z score formula, along with our values for the mean (0) and the standard deviation (1):
Simplifying the right hand side, X-0 = X; X/1 = X. This means X = -1.91.
For the second value,
Simplifying the right hand side, X-0 = X; X/1 = X. This means X = 1.91.
This means the two values are 1.91° and -1.91°.