Out of a sample of 500 newborns, it is found that 475 weigh between 2500g and 4000g. The weights are normally distrusted. Find mean and standard deviation.

Question

Can someone please help me answer this question thank you! 

Answer 1

475/500 = .95. So, you have the data from 95% of your sample, which is normally distributed.

In a Normal curve, 95% of your data lies between -2 and +2 standard deviations from the mean.

 

The mean of your newborns' weight is (2500+4000)/2 = 3250. This is the center of your normal curve.

 

The difference between the mean and -2 standard deviations is 3250-2500 = 750. Divide this by 2 to get your standard deviation of 375.