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DRILL What conditions need to be met when doing an inference test?
What is the difference between a Binomial and Geometric Distribution? If a sample of 200 people showed 34% of the people liked the color blue, how many people like the color blue? AP Statistics, Section 12.1
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Section 12.1 Inference for a Population Proportion
AP Statistics March 22nd 2011
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Parameters vs Statistics
Mean Standard Deviation σ Proportion p Statistics Mean x-bar Standard Deviation s Proportion p-hat AP Statistics, Section 12.1
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What we know about inference
We are trying to make sense about what is happening at the population level by looking at sample data Step 1: “What is the population and the parameter of interest?” We make assumptions in the form of H0 Step 1: “What is H0?” We need to know about the distribution of the sample statistic Step 2: “Is the distribution of sample means normal?” AP Statistics, Section 12.1
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Our inferential work so far…
Has been about the distribution of sample means and the distribution of the difference of sample means. AP Statistics, Section 12.1
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But what about proportions?
We learned in Chapter 9 about the distribution of sample proportions. AP Statistics, Section 12.1
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But what about proportions?
We know that the distribution of sample proportions is approximately normal when these conditions are met… np>10 nq>10 AP Statistics, Section 12.1
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AP Statistics, Section 12.1
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Test of significance A recent study concluded that 25% of all U.S. teenage females have a STD. (This is made up) A recent sample of 500 female teenagers from southeastern Oakland county found the 22% have an STD. Is this strong evidence to suggest that teenage females from SE Oakland county have a lower infection rate than the national average? AP Statistics, Section 12.1
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1: Population, Parameter of Interest, H0 and Ha
3: Calculations Pop/Parameter: Proportion of teenage girls from southeastern Oakland county with an STD. 2: Procedure Name & Conditions 4: Interpret 1-Prop Z-Test SRS: Random but not SRS Proceed with caution! Normality: np & n(1 – p) > 10 Independence: Yes AP Statistics, Section 12.1
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Confidence Intervals AP Statistics, Section 12.1
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Calculate the Confidence Interval
1: Population & Parameter of Interest 3: Calculations 2: Procedure Name & Conditions 4: Interpret AP Statistics, Section 12.1
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Exercises all AP Statistics, Section 12.1
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