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Name: _____________________________________________________________
Date: ________________________
Period: _______
Chapter 14: Probability & Statistics
Topic 4: Intro to Statistics
Statistics is the study and interpretation of numerical data. If only one variable is being analyzed, it is called
_________________ statistics. There are a number of ways that data can be gathered for statistical studies.
Data Gathering Methods:

___________________: used to collect information from a group of people. A survey is an efficient way of
obtaining a wide range of information from a large number of people. Validity of surveys depends on
the honesty of its participants.

___________________: type of survey in which an attempt is made to reach every member of an entire
population. For example, the United States has a census every 10 years to count how many people
are in the country.

___________________: a subset of the entire population. Many times it is not cost-effective or productive to
gather information from an entire population. When this is the case, a sample is used. It is always
important to make sure that the survey sample is representative of the entire population.

___________________: Scientists and engineers use this to determine information about an event. For
example, to determine the amount of weight a bridge can hold, engineers first simulate the effects
statistically on a computer. Then, they use that data to draw conclusions about how the bridge should
be constructed to bear the weight that it will be holding.

___________________: a study that is used to gather information about the effect of some kind of
intervention. For example, medicine or an exercise program. The results obtained in from an
experimental sample are compared to the results from a control sample. A control group is identical
to the experimental group, except without one aspect whose effect is being tested.

___________________: individuals are observed or certain outcomes are measured. Data is gathered
without any intervention. There is no attempt made to affect the outcome.
Bias and Random Sample:
In statistics, it is important to determine if the information that is presented is somewhat ______________. This
is when data used in the sample have come from sources that have a ________________________ ____________________
in the impact of the statistics. When this is the case, the sample is not representative of the general
population, and it is said to be ________________ or ___________________.
In order that the sample reflects the properties of the entire group, the following three conditions must exist:
1. The sample must be ________________________________ of the group being studied.
2. The sample must be __________________ enough to be effective.
3. The selection should be ________________________ or determined in such a way as to ________________________
____________ _________________.
Name: _____________________________________________________________
Date: ________________________
Period: _______
Examples:
1. Car manufactures want to explore the desirability of pre-installed infant seats in their new car designs.
Which of the following groups would be most likely to provide an unbiased sample for a survey?
(1) adult shoppers at a supermarket with young children in shopping carts
(2) couples signing up to win a honeymoon package at a bridal expo
(3) adults visiting a car show
(4) a group of teenagers playing ball at the park
2. A new medicine intended for use by adults is being tested on five men whose ages are 22, 24, 25, 27, and
30. Does the sample provide a valid test?
Measures of Central Tendency:
Measures of central tendency are summary statistics that indicate where the center of a collection of data
lies. Three common measures of central tendency are mean, median, and mode.
Mean:
Think __________________
The mean refers to the arithmetic average of the data and its symbolized as 𝑋̅, read as "x bar." The
mean is the most common measure of central tendency. The mean is the sum of all of the data values
divided by the number of data values.
Median:
Think __________________
The median is the middle number of a data set arranged in numerical order. Therefore, whenever we
are looking for the median, we must write our data in numerical order. To find out which position is
the median, add 1 to the total number of data values and divide by 2. The value in that position,
counting from the first or last term, is the median. If there is no middle term, find the average of the
middle two terms to arrive at your median.
Mode:
Think __________________
The mode is the most commonly repeated data value in a set. Some collections of data, often referred
to as distributions, will have no mode and others will have multiple modes.
Example:
Find the mean, median and mode (round to the nearest tenth if necessary) of a recent 20-point quiz with the
following results:
18, 17, 16, 18, 12, 18, 20, 20, 11, 10, 15.