Chapter 1

deals with the collection, analysis, interpretation, and presentation of data. is the study of randomness and deals with chance occurrences. Statistics deals with the collection, analysis, interpretation, and presentation of data. Probability is the study of randomness and deals with chance occurrences.

KEY TERMS n Experiment: process of finding out the average time spent at a CC before transferring n Population: CC students at a particular school who transfer n Parameter: Average time spent at the CC by all students who transfer Example: Average time spent at a Community College (CC) before transferring to a 4-year school

Key Terms n Sample: A survey of these students n Statistic: Average time spent by that survey of students n Variable (in words): Let X = time spent by one student at a CC before transferring. n Data: A value representing the time in years, quarters, semesters, etc.

Another Example n Experiment: process of finding the proportion of CA teenagers who drink milk each day n Population: All CA teenagers n Sample: 25 teenagers in a CA shopping mall n Parameter: Proportion of CA teenagers who drink milk each day in the population n Statistic: Proportion of CA teenagers who drink milk in the sample n Variable: X = the number of CA teenagers who drink milk each day n Data: 6 CA teenagers (out of the 25) drink milk each day Review Ex. 1-1 in Ch. 1 after class. Cover up answers and then check.

DATA n Qualitative: Categorical (words) Ex. Blood type, color, names n Quantitative: Numerical Discrete - countable answers “How many?” Continuous - measured answers “How much?” Examples: Age weight of backpack # of classes you take favorite soccer team town you live in school population

Sampling n To gather information about the entire population often costs too much money and is impossible.

Is sampling OK? Ex: Do we drain blood to do a test? Do we poke all over a cake to test for doneness? Consider the 1990 census that was done in the United States.

The key is correct sampling! Ex. We are interested in the average number of hours per day that U.S. 4th graders watch T.V. Do we survey n all latch key 4th graders? NO n all 4th graders who play organized sports? NO n a variety of 4th graders all over the country? YES

Incorrect Sampling Ex. Truman versus Dewey In the late 1940’s, a presidential survey was done by telephone. The people who did the survey took the names from a conservative magazine subscription list.

Variation in Data and Samples n Roll a fair die 20 times. Record how many times each face occurs. n Do the experiment a second time. n Which experiment had the correct results?

Methods of Sampling n Simple random n Systematic n Cluster n Stratified n Convenience

Sampling may be done with or without replacement. n With replacement: Flip 2 fair coins 25 times and record the number of heads. n From your class, randomly pick 3 people to form a collaborative group.

Frequency, Relative Frequency, and Cumulative Relative Frequency n Frequency (freq. or F): How many times an answer occurs n Relative Frequency (RF): The percent, decimal, or fraction an answer occurs, n Cumulative Relative Frequency (cum. RF): Accumulation of the percent that occurred at that value or lower

Ex. Age of students (in years): 21, 26, 35, 35, 19, 22, 56, 44, 23, 26, 22, 39 A table that organizes the data.

Questions n What is the relative frequency of 22 or 26 years? n What percent of students are less than 30 years? n What fraction of students are from 22 to 29 years, inclusive?

Ex. Age of students (in years): 21, 26, 35, 35, 19, 22, 56, 44, 23, 26, 22, 39 A different way of creating the table.

Ex. Nineteen people were asked how many miles, to the nearest mile, they commute to work each day. The data are 2, 5, 7, 3, 2, 10, 18, 15, 20, 7, 10, 18, 5, 12, 13, 12, 4, 5, 10.

Questions n Comment on the table. Is it correct? Assume the data are correct. n T or F. Three percent of the people surveyed commute 3 miles. Why or why not is this true? n What fraction of people surveyed commute 5 or 7 miles n What percent of the people surveyed commute 12 miles or more?