13_(Ch12)_Estimation_Outline

13_(Ch12)_Estimation_Outline - 11/23/10 1 2 3 4 5 6 7 8 9...

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Unformatted text preview: 11/23/10 1 2 3 4 5 6 7 8 9 10 11 12 Psychological Statistics - Estimation PSY 207 Overview •  Estimation – Point estimation – Interval estimation – Confidence intervals •  Constructing confidence intervals •  Sample size and confidence intervals •  Confidence vs. Precision Estimation •  We have previously discussed testing hypotheses about a population •  We may also be interested in estimating a population mean... – ... to determine the size of an effect – ... to determine information about a population •  We can use sample characteristics and test statistics to estimate population means Two types of estimates Point estimates Interval estimates Confidence Intervals •  Range of values within which we are reasonably confident the population mean lies. •  In fact, we can specify exactly how confident we are. Interval estimates based on t Sampling distribution of the mean Steps for a confidence interval 1.  Calculate sample characteristics: 1.  Sample mean 2.  Sample variance 2.  Select an acceptable confidence level (e.g. 95%). 3.  Calculate the standard error. 4.  Find the corresponding t-values. 5.  Use the formula to calculate the confidence interval. Example What it means to be confident 1 13 11/23/10 11 12 13 14 15 16 17 18 Example What it means to be confident •  For a 80% confidence interval, – if a series of confidence intervals were constructed, 80% of the intervals will contain the population mean – 20% of all intervals will be false. What it means to be confident •  Typically, we only choose one confidence interval. •  For a 80% confidence interval, the one interval that we actually computed has a 20% chance of not containing the population mean. Sample size and confidence intervals Interval estimates Example Precision vs. Confidence Sampling distribution of the mean 2 ...
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This note was uploaded on 08/22/2011 for the course PSY 207 taught by Professor Pfordesher during the Fall '07 term at SUNY Buffalo.

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13_(Ch12)_Estimation_Outline - 11/23/10 1 2 3 4 5 6 7 8 9...

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