Question

IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. A sample of 13 people is selected at random.

Find the probability that the mean IQ of people in the sample is greater than 105

Answer 1

When describing data, always start with a graphical representation.

 Graphs help identify the overall distribution pattern. Looking at a graph

makes it visually clear how spread a variable is, which values occur most

frequently, and whether or not the distribution is skewed.

 Next, obtain more precise information by providing a numerical summary of

the data using the mean, median, range, five-number summary, and any

other appropriate information.

 Some distributions are so regular that they can be described by a smooth

curve. Real data are represented in a histogram. Curves represent a symbol,

or an abstract version of a distribution.