Give one example of how bias could occur in asample survey.

The table below gives a probability model for the distribution of total household income in the U.S. (based onCurrent Population Survey)

Total Household Income Probability

Under $25,000. 0.223

$25,000 to $49,999 0.188

$50,000 to $74,999 0.138

$75,000 to $99,999 0.179

$100,000 or over 0.272

What is the probability that a randomly chosen household will have a total income of at least $75,000?

44% of Americans have type O blood. Suppose 4 people are chosen at random from the American population. What is the probability that all 4 have type O blood?

(Enter answer with 4 places after the decimal)

The reading speed of second grade students is approximately normal, with a mean of 90 words per minute (wpm) and a standard deviation of 10 wpm.

What is the probability that a random sample of 24 second grade students results in a mean reading rate of more than 95 words per minute?

Enter your answer with 4 places after the decimal.

A random sample of 1003 adult Americans was asked, "Do you pretty much think televisions are a necessity or a luxury you could do without?" Of the 1003 adults surveyed, 521 indicated that televisions are a luxury they could do without.

Construct a 95% confidence interval for the population proportion of adult Americans who believe that televisions are a luxury they could do without.

Enter themargin of errorof the interval. Use three places after the decimal. Show your work in the next question.

In the Spacelab Life Sciences 2 payload 14 male rats were sent to space. Upon their return, the red blood cell mass (in milliliters) of the rats was determined. A control group of 14 male mats was held under the same conditions (except for space flight) as the space rats, and their red blood cell mass was also determined when the space rats returned.

The results are as follows:

Groupn

x

sFlight147.881.02Control148.431.01

Does the evidence suggest that the flight animals have a different red blood cell mass from the control animals at the

= 0.05 level of significance? (You may assume the levels are approximately normal.)