Clara recorded 50 numerical observations on a certain variable and then calculated the mean x‾x and the standard deviation s for the observations. To help decide whether a normal model is appropriate, she created the following chart.

In Clara's chart, the letters a, b, c, d, and e represent the number of observations falling in each interval. Which of the following list of counts for a, b, c, d, and e respectively, is the best indicator that the variable can be modeled with a normal approximation? Clara recorded 50 numerical observations on a certain variable and then calculated the mean x‾x and the standard deviation s for the observations. To help decide whether a normal model is appropriate, she created the following chart.

In Clara's chart, the letters a, b, c, d, and e represent the number of observations falling in each interval. Which of the following list of counts for a, b, c, d, and e respectively, is the best indicator that the variable can be modeled with a normal approximation? STATISTICSNew chemicals are screened to see of they cause cancer in lab mice. A "bioassay" can be done with 500 mice: 250 are chosen at random and given the test chemical in their food, the other 250 get a normal lab diet. After 33 months, cancer rates in the two groups are compared, using the two-sample z-test. Investigators look at cancer rates in about 25 organs and organ systems ---lungs, liver, circulatory system, etc. With one chemical,
$$
z \approx - 1.8
$$
for the lungs,
$$
z \approx 2.4
$$
for the liver,
$$
z \approx - 2.1
$$
for leukemia, and there are another 22 values of z that range from
$$
- 1.6 \text { to } + 1.5
$$
. The investigators conclude that the chemical causes liver cancer
$$
( z \approx 2.4 , P \approx 1 \% , \text { one-tailed) }
$$
. Comment briefly. 5th EditionDaniel S. Yates, Daren S. Starnes, David Moore, Josh Tabor2,433 solutions

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