The lengths of pregnancies are normally distributed with a mean of 267 days and a standard deviation of 15 days. a. find the probability of a pregnancy lasting 309 days or longer. b. if the length of pregnancy is in the lowest 4%, then the baby is premature. find the length that separates premature babies from those who are not premature.

We have a normal distribution with a mean of 267 days and a standard deviation of 15 days. To solve this proble we're going to need the help of a calculator.

a. The probability of a pregnancy lasting 309 days or longer is:

P(z>309) = 0.0026 or 0.26%

b. The lowest 4% is separeted by the 240.74 days. The probability of pregnancy lasting 240.74 days is 4%.

a) 0.26% probability of a pregnancy lasting 309 days or longer.

b) A pregnancy length of 241 days separates premature babies from those who are not premature.

Step-by-step explanation:

Problems of normally distributed samples can be solved using the z-score formula.

In a set with mean and standard deviation , the zscore of a measure X is given by:

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

a. Find the probability of a pregnancy lasting 309 days or longer.

This is 1 subtracted by the pvalue of Z when X = 309. So

has a pvalue of 0.9974

So there is a 1-0.9974 = 0.0026 = 0.26% probability of a pregnancy lasting 309 days or longer.

b. If the length of pregnancy is in the lowest 4%, then the baby is premature. Find the length that separates premature babies from those who are not premature.

This is the value of X when Z has a pvalue of 0.04. So X when Z = -1.75

A pregnancy length of 241 days separates premature babies from those who are not premature.

solution:

as, mean is defined as sum of all the observations divided by total number of observations.

and , median is mid value of the data whether arranged in ascending order or descending order.

consider, roadsters:

2,3,4,5,6,7,8,9

mean =

also, median= , because number of observations is even, so median is mean of two mid values.

now, coming to bandits

2,3,4,5,6

mean =  

median = 4, as number of observations is odd.

so, roadsters has greater median as well mean than bandits.

→option a is true about the repairs performed on 2 types of cars:

bandits have lower median and mean than roadsters.

need more info

step-by-step explanation: