1、统计 基础 和 prism软件使用仝鑫 魏健2015-12目录线性回归和 prism软件应用t检验、 F检验（方差分析）和 prism软件应用假设检验（参数检验和非参数检验）统计学基础知识The Gaussian Distribution The Gaussian function describing this shape is defined as follows:where m represents the populationmean and s the standard deviation.Few biological distributions, if any, really fo
2、llow the Gaussian distribution一、统计学基础知识The Central Limit TheoremIf your samples are large enough, the distribution of means will follow a Gaussian distribution even if the population is not Gaussian.N=10 or so is generally enough一、 统计量（ Descriptive Statistics：column statistics in prism）Measures of L
3、ocationA typical or central value that best describes the data（ central tendency） . Mean（平均值） Median（中数） Mode(众数） Geometric mean(几何均数 )Measures of DispersionDescribe spread (variation) of the data around that central value. Range（范围） Variance（方差） Standard Deviation（标准偏差） Standard Error（样本间标准误 =SD/n
4、Coefficient of variation（变异系数） Confidence Interval（置信区间）No single parameter can fully describe distribution of data in the sample. Moststatistics software will provide a comprehensive table describing the distribution.Measures of Location: MeanMean More commonly referred to as “the average”. It is t
5、he sum of the data points divided by the number of data points.Migration AssayCell # Distance travelled(Microns)1 492 273 1324 245 786 807 628 399 200M=76.78 microns = 77 micronsMeasures of Dispersion: VarianceVariance Defined as the average of the square distance of each value from the mean.To calc
6、ulate variance, it is first necessaryto calculate the mean score then measurethe amount that each score deviates fromthe mean. The formula for calculating variance is:Measures of Dispersion:Standard DeviationStandard Deviation The most common and useful measure of dispersion. Tells you how tightly e
7、ach sample is clustered around the mean. When the samples are tightly bunched together, the Gaussian curve is narrow and the standard deviation is small. When the samples are spread apart, the Gaussian curve is flat and the standard deviation is large. The formula to calculate standard deviation is:
8、SD = square root of the variance.标准偏差（ SD） 和标准误（ SEM）Standard deviation refers to the amount you expect an individual measurement to vary from the average.标准差（ standard deviation）衡量的是样本值对样本平均值的离散程度，反应个体间变异的大小，是量度数据精密度的指标。Standard error of the mean is how much you expect a value averaged from several
9、 measurements to vary from the true mean. 标准误（ standard error）衡量的是样本平均值对总体平均值的离散程度，反映抽样误差的大小 ,是量度结果精密度的指标。Should we show standard deviation or standard error?Use Standard Deviation If the scatter is caused by biological variability and you want to show that variability. For example: You aliquot 10 p
10、lates each with a different cell line and measure integrin expression of each.Use standard error If the variability is caused by experimental imprecision and you want to show the precision of the calculated mean. Then show the 95% confidence interval of the mean. For example: You aliquot 10 plates of the same cell line and measure integrin expression of each.
