7. Students did poorfy on a recent test, so their teacher decided to add 6 points to each student's grade. Which of the following statistical measures would not be affected by the arldition of these points?
1) the mean score
2) the first quartiles
3) the median score
4) the standard deviation of the scores
8. In 2013, the mean gas mileage for cars was 27,6 miles per gallon, If the distribution of gas mileage in cars is normal with a standard deviation of 3.8 miles per gallon, then what percent of cars had gas mileages between 20 and 30 miles por gallon?
9. The gestation time (number of days before birth) for cows is normally distributed with a mean of 284 days and a standard deviation of 12 days. At a local ranch, over the course of a year there are 820 calf births. Of these, how many would be expected to have a gestation time less than 270 days?
1) 12
2) 78
3) 100
4) 237
10. A company wishes to determine the cooking time for rice. The company's technician cooked 2 cups of rice and recorded the time needed for the rice to be reacty to eat. Repeating this process 35 times resulted in an approximately normal distribution, with a mean of \( 20: 37 \) minutes and a standard deviation of 1.5 minutes. Write an interval in which the middle \( 95 \% \) of cooking times should fall. (Rounds to the nearest hundredth)
11. In a recent poll of 400 likely voters, \( 35 \% \) of them preferred Candidate A. To the nearest tenth, what would be the margin of error of this statistic?
12. On a standardized test where the results are distributed normally, Josie scored a 250 . If the mean score was a 170 with a standard deviation of 30 , then what is Josie's percentile rank rounded to the nearest whole percent? Explain how you arrived at your answer.