# The average weight of a child is 22 pounds with a standard deviation of 3 pounds. Assuming that the weight of babies are normally distributed, what is the weight of the baby if she is in the 70th...

The average weight of a child is 22 pounds with a standard deviation of 3 pounds. Assuming that the weight of babies are normally distributed, what is the weight of the baby if she is in the 70th percentile ?

*print*Print*list*Cite

### 1 Answer

The average weight is given as 22lbs with a population standard deviuation of 3lbs. Assuming a normal distribution of weights, what is the weight at the 70th percentile?

We use a standard normal z-table to find the z-score such that 70% lies to the left of it. The corresponding z-score is z=0.52 (from a TI-8x calculator the value is z= .5244005101)

To find the corresponding x-score we substitute the known values into z=(x-mean)/(std dev)

0.52=(x-22)/3

1.56=x-22

x=23.56 lbs

----------------------------------------------------------------------------------------

The weight at the 70th percentile is approximately 23.6lbs

----------------------------------------------------------------------------------------