Question

The Polk company reported that the average age of cars on road in recent year was 7.5 vears. Suppose the distribution ofages of cars on road is approximately bell-shaped. If 99.7% of the ages are bctween I and l4 vears what is the standard deviation of car age? Supposc the standard deviation is 1.7 years and the mean is 7.5 years.etween what two valucs would 95% of the car ages fall?​

Answer 1

Answer:

The Polk Company reported that the average age of a car on U.S. roads in a recent year was 7.5 years. (a) Suppose the distribution of ages of cars onU.S. roads is approximately bell-shaped. If 99.7% of the ages are between 1 year and 14 years, what is the standard deviation of car age? (b) Suppose the standard deviation is 1.7 years and the mean is 7.5 years. Between what two values would 95% of the car ages fall? (a) Round the answer to 3 decimal places (the tolerance is +/- 0.005). = (b) Round the answer to 1 decimal place (the tolerance is +/-0.5). Supposing that = 1.7: between and lie 95% of the values. The time needed to assemble a particular piece of furniture with experience is normally distributed with a mean time of 43 minutes. If 68% of the assembly times are between 40 and 46 minutes, what is the value of the standard deviation ( )? Suppose 99.7% of the assembly times are between 35 and 51 minutes and the mean is still 43 minutes.What would the value of the standard deviation be now ( )? Suppose the time needed to assemble another piece of furniture is not normally distributed and that the mean assembly time is 28 minutes.What is the value of the standard deviation if at least 77% of the assembly times are between 24 and 32 minutes ( )? Keep 2 decimal places where necessary. = , = , = The tolerance is +/- 0.05.