Stats Review

It means that three-tenths of the plaque is removed.

 It's nonsense, because plaque is a categorical

     variable, so percents don't make sense.

It's nonsense, because removing 100 percent of

    the plaque already removes all of it.

It means that there is 3 times as much plaque

    before using the rinse as there is after using it.

An ad for a new mouth rinse says that it

"reduces plaque on teeth by 300%".  What

does this mean?

You measure the age (years), weight (pounds), and marital

status (single, married, divorced, or widowed) of 1400 women.

How many variables did you measure?





In January of 1997, the price of Intel common stock rose from $131 per share

to $162 per share. (Intel makes the processors for the computers you have been

 happily using.) What percent increase is this?





Michelle's income two years ago was $420,000. Last year her income was

only $100,000. The percent change in Michelle's income was

76.2% decrease

 320% decrease 

31.3% decrease

None of these

The telephone company says that 62% of all residential phone

 numbers in Los Angeles are unlisted. A telephone survey contacts

a random sample of 1000 Los Angeles telephone numbers,

of which 58% are unlisted. In this setting,


62% is a parameter and 58% is a statistic

58% is a parameter and 62% is a statistic

62% and 58% are both parameters

 58% and 62% are both statistics
In a table of random digits,

 a specific pair such as 00 cannot be repeated until all

      other pairs have appeared

the pair 00 can appear, but 000 is not random and can

     never appear in the table

any pair of entries is equally likely to be any of the

     100 possible pairs 00, 01, 02, . . . , 99

each pair of digits 00, 01, 02, . . . , 99 appears exactly

     once in any row of the table

Your statistics class has 30 students. You want to call an SRS

 of 5 students from your class to ask where they use a computer

for the online exercises. You label the students 01, 02, . . . , 30.

You enter the table of random digits at this line:


14459 26056 31424 80371 65103 62253 22490 61181


Your SRS contains the students labeled

 14, 45, 92, 60, 56

14, 31, 03, 10, 22

14, 03, 10, 22, 22

14, 03, 10, 22, 06

When we take a census, we attempt to collect data from

a stratified random sample

a convenience sample

 every individual selected in a simple random sample

every individual in the population

A national sample survey interviewed 3,800 people age 18 and

older nationwide by telephone. One question asked was whether

they agreed with this statement: "Some people say we should

have a third major political party in this country in addition to

the Democrats and Republicans."


53% of the people asked agreed that we should

have a third party. The number 53% is a

margin of error


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