3. Describing Data Numerically

Given the sample data set consisting of a single value $8$, what is the variance of the sample?

"The Empirical Rule SAT Math scores have a bell-shaped distribution with a mean of 515 and a standard deviation of 114.

Source: College Board

a. What percentage of SAT scores is between 401 and 629?"

Graphical Analysis In Exercises 21–24, you are asked to compare three data sets.

(c) Estimate the sample standard deviations. Then determine how close each of your estimates is by finding the sample standard deviations.

i.

ii.

iii.

[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.

Suppose you have two histograms, A and B, each representing the distribution of exam scores for two different classes. Histogram A shows scores tightly clustered around the mean, while Histogram B shows scores spread out over a wider range. Which histogram depicts a higher $standard deviation$?

In Exercises 13 and 14, find the range, mean, variance, and standard deviation of the population data set.

Drunk Driving The number of alcohol-impaired crash fatalities (in thousands) per year from 2010 through 2019 (Source: National Highway Traffic Safety Administration)

10.1 9.9 10.3 10.1 9.9 10.3 11.0 10.9 10.7 10.1

Suppose you have two histograms, $A$ and $B$, each representing the distribution of exam scores for two different classes. Histogram $A$ shows scores tightly clustered around the mean, while Histogram $B$ shows scores spread out over a wider range. Which histogram depicts a higher standard deviation?

For each of the following data sets, decide which has the higher standard deviation (set 1 or set 2), if any, without doing any computation. Explain the rationale behind your choice. Then, verify your choice by computing the standard deviation by hand.

Percentiles. In Exercises 17–20, use the following radiation levels (in W/kg) for 50 different cell phones. Find the percentile corresponding to the given radiation level.

0.48 W/kg

Find the standard deviation of the sample below. Round your answer to the nearest tenth.

$Which\; of\; the\; following\; groups\; of\; scores\; would\; have\; the\; smallest\; standard\; deviation?$

In Exercises 1 and 2, use the following wait times (minutes) at 10:00 AM for the Tower of Terror ride at Disney World (from Data Set 33 “Disney World Wait Times” in Appendix B).

35 35 20 50 95 75 45 50 30 35 30 30

c. Find the standard deviation s.

"[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."

A sample of $n=5$ scores has a mean of $m=20$ and a sample variance of $s^2=4$. What is the sample standard deviation?