Biology 2244A/B Chapter Notes - Chapter 17: Standard Deviation, Statism, Confidence Interval
25 Dec 2016
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Confidence interval: uses sample data to estimate an unknown population parameter with an indication of how accurate the estimate is, and of how confident we are that the result is correct. Confidence intervals and tests of significance for population mean of a normal population. In practice: we don"t know so substitute standard error for standard deviation. T statistic: same interpretation as any standardized statistic. How far x| is from u in standard deviation units. If we knew population standard deviation we would base confidence intervals on the on sample z statistic. Sample standard deviations: better estimation of population standard deviation with increasing sample size. Degrees of freedom (df): specifies a particular t distribution. Sample estimeation: introduces more variation into the statistic. Increasing degrees of freedom: causes density curve to approach n(0,1) S: estimates more accurately to as sample size increases. As we replace population standard deviationwith sample standard deviation.
