The weights of ripe watermelons grown at Mr. Smith's farm are normally distributed with a standard deviation of 2 lb. Find the mean weight of Mr. Smith's ripe watermelons if only 5% weigh less than 18 lb. (Give your answer correct to one decimal place.)

Question

The weights of ripe watermelons grown at Mr. Smith's farm are normally distributed with a standard deviation of 2 lb. Find the mean weight of Mr. Smith's ripe watermelons if only 5% weigh less than 18 lb. (Give your answer correct to one decimal place.) 
  lb 
Can someone help with the formula and I want to attempt to work it out.

Tom 614 · Accepted Answer

I have worked several times this is my last try and I got (18-.5199)/2=8.74005=8.7

PsyDAG · Answer

Z = (score-mean)/SD = (18-mean)/2

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.05) and its Z score. Insert in equation above and solve for mean.

Tom614 · Answer

When I worked out this is what I came up with..(31.55-31.5)/0.003= 16.66666 = 16.6667