A study records each participant's blood type and systolic blood pressure in mm Hg. How are those two variables classified?

A sample of commute times in minutes is 12, 15, 20, 22, 23, 26, 31, 35. Using the median-of-halves method, what is the IQR?

A principal uses the mean backpack mass from 80 sampled students to estimate the mean backpack mass for all students at the school. What is that sample mean?

Use the dot plot of 15 quiz scores. What is the median score?

Use the stem-and-leaf plot of plant heights. What is the smallest height shown?

Use the histogram of homework time. How many students spent at least 20 but less than 30 minutes?

Two class box plots have the same median test score, but Class A has a much wider box than Class B. What does that show?

Clinic wait times have a long right tail because a few patients waited much longer than the rest. What shape describes this distribution?

Use the box plot of bus wait times. What feature of the distribution is shown?

A library chooses a random starting visitor, then surveys every 10th visitor entering the building. What sampling method is this?

An online lunch poll invites anyone at a school to respond, and most replies come from students angry about lunch. What problem is most likely?

A school survey is given only during homeroom, so students absent that day have no chance to be selected. What sampling problem is this?

A researcher randomly assigns 60 garden plots to one of three fertilizers, with 20 plots per fertilizer. What design is being used?

To compare two study apps, each student uses both apps in random order, and the score difference for that student is recorded. What design is this?

Students are grouped by grade, then randomly assigned to tutoring or no tutoring within each grade. What role does grade play?

For two events in a clinic, $P(A)=0.45$, $P(B)=0.30$, and $P(A\cap B)=0.12$. What is $P(A\cup B)$?

On a winter day, $P(\text{rain})=0.25$ and $P(\text{snow})=0.10$. If rain and snow are mutually exclusive, what is the probability of neither?

A machine has probability 0.08 of failing during a shift. What is the probability it does not fail during that shift?

Of 400 athletes, 160 play soccer, 100 run track, and 50 do both. To three decimals, what is the probability a soccer player also runs track?

Of 500 students, 200 take band, 150 take art, and 60 take both. Are band and art independent?

For factory parts, $P(D)=0.04$, $P(L)=0.10$, and $P(D\cap L)=0.004$, where D means defective and L means late. Are D and L independent?

A spinner lands on blue with probability 0.20 on each independent spin. In 10 spins, what is the probability of exactly 3 blues, to three decimals?

A game ticket costs $1. It pays $5 with probability 0.30 and pays $0 otherwise. What is the expected net gain per ticket?

A player makes a free throw with probability 0.75 independently each time. In 6 shots, what is the probability of at least one miss, to three decimals?

Test scores are normal with $\mu =70$ and $\sigma =8$. Given that the area below $z=-1$ is 0.1587, what is $P(X<62)$ to three decimals?

Apple masses are normal with $\mu =150$ g and $\sigma =10$ g. Given that 0.6827 of a normal curve lies between $z=-1$ and $z=1$, what is $P(140<X<160)$?

A population of package masses has $\sigma =12$ kg. For random samples of size $n=36$, what is the standard deviation of the sampling distribution of $\bar{x}$?

For random samples of 200 voters from a population with $p=0.55$, is the sampling distribution of $\hat{p}$ approximately normal?

For random samples of 400 voters from a population with $p=0.30$, what are the mean and standard deviation of $\hat{p}$, to three decimals?

A random sample of 500 voters has 310 in favor of a measure, and $z^{\ast }=1.96$. To three decimals, what is the 95% confidence interval for the population proportion?

In a random sample of 80 seeds, 68 sprout, and $z^{\ast }=1.96$. To three decimals, what is the 95% confidence interval for the true sprouting proportion?

A 92% confidence interval for the proportion of all school parents who support a calendar change is 0.41 to 0.49. What is the correct interpretation?

A seed maker claims $p=0.60$ of seeds sprout. In a test of 150 seeds, 78 sprout. What is the one-proportion z statistic?

A test of $H_0:p=0.25$ against $H_a:p>0.25$ gives a p-value of 0.018. What does that p-value mean?

For $H_0:p=0.50$ against $H_a:p\ne 0.50$, a one-proportion z test gives p-value 0.032. At $\alpha =0.05$, what conclusion is appropriate?

Sample A has 54 successes in 180 trials, and sample B has 42 successes in 120 trials. What pooled proportion is used for a two-proportion z test of equal proportions?

School 1 has 90 of 150 students favoring uniforms; School 2 has 72 of 160. With $z^{\ast }=1.96$, what 95% confidence interval estimates $p_1-p_2$?

Students at 3 clinics are sampled separately and classified into 4 outcome categories. How many degrees of freedom does the chi-square test for homogeneity use?

A chi-square test of independence for grade level and club participation gives chi-squared = 8.4, df = 2, and p-value = 0.015. At $\alpha =0.05$, what conclusion is appropriate?

A random sample of 16 protein bars has mean mass 22.4 g and $s=3.2$ g. With $t^{\ast }=2.131$, what is the 95% margin of error?

A random sample of 25 bottles has mean fill 5.8 L and $s=1.5$ L. With $t^{\ast }=2.064$, what is the 95% confidence interval for $\mu$?

A 95% confidence interval for the mean bus travel time for all students is 12.1 to 14.7 minutes. What is the correct interpretation?

A sample of 10 water samples has mean nitrate 18.6 mg/L and $s=2.0$ mg/L. Testing $H_0:\mu =20$, what is the one-sample t statistic?

In a paired running study with 12 runners, the mean difference after-before is -1.8 seconds and $s_d=2.4$ seconds. Testing $H_0:{\mu }_d=0$, what is t?

A one-sample t test of $H_0:\mu =50$ against $H_a:\mu >50$ gives p-value 0.087. At $\alpha =0.05$, what conclusion is appropriate?

Group 1 has $n=20$, $\bar{x}=14.5$, $s=3.0$. Group 2 has $n=18$, $\bar{x}=12.9$, $s=2.4$. What is the standard error for ${\bar{x}}_1-{\bar{x}}_2$?

Class A has $n=25$, $\bar{x}=78$, $s=8$; Class B has $n=20$, $\bar{x}=74$, $s=6$. With $t^{\ast }=2.02$, what interval estimates ${\mu }_A-{\mu }_B$?

Researchers compare mean lead levels in water from two independent random samples of homes in City A and City B, with population sigmas unknown. What procedure fits?

Use the scatterplot of outside temperature and heating cost for homes. What relationship is shown?

Across 18 delivery vans, engine age and fuel efficiency have $r=-0.82$. What does this value say?

Across 12 doses, symptom score first decreases and then increases, making a clear U-shaped relationship. What does a correlation near $r=0$ mean here?

A regression predicts plant height in centimeters from fertilizer in grams: $\hat{y}=12.4+0.85x$. What does the slope mean?

Use the regression output for predicting final exam score from hours studied. What is the slope in context?

A model predicts bus wait time in minutes from the number of stops before downtown: $\hat{y}=4.2+1.6x$. What is the predicted wait for $x=5$ stops?

A delivery took 42 minutes, while the regression model predicted 38 minutes. What is the residual?

Use the residual plot for the crop-yield model. What does the residual plot suggest about the linear model?

Use the residual plot for delivery time. What does the residual plot suggest about the linear model?

A regression of algae mass on sunlight hours has $r=0.70$. What percent of variation in algae mass is accounted for by the linear model?

Use the scatterplot of taxi trip distance and cost. What point is likely to have the most influence on the least-squares line?

A regression output reports $r^2=0.64$ for predicting corn yield from rainfall. What does this mean?