Recall from Chapter 7 that the interquartile range (IQR) covers the middle 50% of the data.
a. What range of standardized scores is covered by the interquartile range for normally distributed populations? In other words, what are the standardized scores for the lower quartile (the 25th percentile) and the upper quartile (the 75th percentile)?
b. How many standard deviations are covered by the interquartile range for a normally distributed population?
c. Data values are outliers for normally distributed data if they are more than two IQRs away from the mean. At what percentiles (at the upper and lower ends) are data values considered outliers for normally distributed data? Use your answers to parts (a) and (b) to help you determine the answer to this question. (Software required.)