3. Describing Data Numerically

The ________ represents the number of standard deviations an observation is from the mean.

The following data represent the length of time (in minutes) between eruptions of Old Faithful in Yellowstone National Park.

b. Approximate the standard deviation length of time between eruptions.

"[DATA] Putting It Together: Paternal Smoking It is well-documented that active maternal smoking during pregnancy is associated with lower-birth-weight babies. Researchers wanted to determine if there is a relationship between paternal smoking habits and birth weight. The researchers administered a questionnaire to each parent of newborn infants. One question asked whether the individual smoked regularly. Because the survey was administered within 15 days of birth, it was assumed that any regular smokers were also regular smokers during pregnancy. Birth weights for the babies (in grams) of nonsmoking mothers were obtained and divided into two groups, nonsmoking fathers and smoking fathers. The given data are representative of the data collected by the researchers. The researchers concluded that the birth weight of babies whose father smoked was less than the birth weight of babies whose father did not smoke.

e. Determine summary statistics (mean, median, standard deviation, quartiles) for each group."

Exit Velocity Use the frequency distribution whose class width is 4 obtained in Problem 25 in Section 2.2 to approximate the mean and standard deviation exit velocity. Compare these results to the actual mean and standard deviation exit velocity.

Travel Time Use the results of Problem 22 in Section 3.1 and Problem 22 in Section 3.2 to compute the z-scores for all the students. Compute the mean and standard deviation of these z-scores.

Answer the following based on the histograms shown in the next column.

a. Which measure of central tendency would you recommend reporting for the data whose histogram is shown in Figure I? Why? b. Which one has more dispersion? Explain.

[NW] [DATA] TelevisionsIn the Sullivan Statistics Survey I, individuals were asked to disclose the number of televisions in their household. In the following probability distribution, the random variable X represents the number of televisions in households.

d. Find the standard deviation of the random variable X.