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Chapter Seven Introduction to Sampling Distributions Section 1 Sampling Distribution. Key Points. Review such commonly used terms as random sample, relative frequency, parameter, statistic, and sampling distributions
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Chapter Seven Introduction to Sampling Distributions Section 1 Sampling Distribution
Key Points • Review such commonly used terms as random sample, relative frequency, parameter, statistic, and sampling distributions • From raw data, construct a relative frequency distribution for x-bar values and compare the result to a theoretical sampling sitribution
Review of Statistical Terms • Population • Sample • Parameter • Statistic
Population the set of all measurements (either existing or conceptual) under consideration
Sample a subset of measurements from a population
Statistic a numerical descriptive measure of a sample
Parameter a numerical descriptive measure of a population
We use a statistic to make inferences about a population parameter.
Principal types of inferences • Estimate the value of a population parameter • Formulate a decision about the value of a population parameter • Make a prediction about the value of a statistical variable.
Sampling Distribution a probability distribution for the sample statistic we are using
Example of a Sampling Distribution Select samples with two elements each (in sequence with replacement) from the set {1, 2, 3, 4, 5, 6}.
Constructing a Sampling Distribution of the Mean for Samples of Size n = 2 List all samples and compute the mean of each sample. sample: mean: sample: mean {1,1} 1.0 {1,6} 3.5 {1,2} 1.5 {2,1} 1.5 {1,3} 2.0 {2,2} 4 {1,4} 2.5 … ... {1,5} 3.0 There are 36 different samples.
Sampling Distribution of the Mean p 1.0 1/36 1.5 2/36 2.0 3/36 2.5 4/36 3.0 5/36 3.5 6/36 4.0 5/36 4.5 4/36 5.0 3/36 5.5 2/36 6.0 1/36
Sampling Distribution Histogram | | | | | | | | | | | | 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
Pinedale Related Review Problems Pinedale, Wisconsin, is a rural community with a children’s fishing pond. All fish caught under 6 inches in length must be released. 100 children are selected and the lengths of 5 fish they caught are recorded along with the mean length of the 5 fish for each child.
Pinedale Related Review Problems What type of measurement is the mean of the average recorded fish lengths for the 100 children? -The mean is a statistic because it is from a sample of fish lengths
Pinedale Related Review Problems How can the relative frequencies of the individual fish length means be used to help us estimate probabilities occurring in the sampling distributions of fish lengths? -Relative frequencies are measures or estimates of the likelihood of a certain statistic falling within the class bounds.