癣疥之疾紫微星在未宮课件.ppt

* Thursday, October 3 Variability nominal ordinal interval nominal ordinal interval Range Interquartile Range Variance Standard Deviation Range Range Interquartile Range X _ Population Sample X μ _ The population mean is μ. The sample mean is X. _ Population Sample X μ _ The population mean is μ. The sample mean is X. The population standard deviation is ?, the sample sd is s. _ ? s SS Variance of a population, ?2 (sigma squared). It is the sum of squares divided (SS) by N N ?2 = SS Variance of a population, ?2 (sigma squared). It is the sum of squares divided (SS) by N N ?2 = ? (X – ? ) 2 SS The Standard Deviation of a population, ? It is the square root of the variance. N ? = This enables the variability to be expressed in the same unit of measurement as the individual scores and the mean. Population Sample X μ _ The population mean is μ. The sample mean is X. _ Population Sample X μ _ The population mean is μ. The sample mean is X. The population standard deviation is ?, the sample sd is s. _ ? s Population SampleA XA μ _ SampleB XB SampleE XE SampleD XD SampleC XC _ _ _ _ In reality, the sample mean is just one of many possible sample means drawn from the population, and is rarely equal to μ. Population SampleA XA μ _ SampleB XB SampleE XE SampleD XD SampleC XC _ _ _ _ In reality, the sample mean is just one of many possible sample means drawn from the population, and is rarely equal to μ. ? sa sb sc sd se Sampling error = Statistic - Parameter Sampling error for the mean = X - μ _ Sampling error for the standard deviation = s - ? *