LFS 252 Lecture Notes - Interquartile Range, Regression Analysis, Standard Score
Document Summary
Lecture 3 center and spread of distributions for numerical variables. For skewed right histogram, the means is to the right of the typical value. Large sd: the distribution ( bell shape) is wide and short in the center; small sd: the distribution is narrow and high in the center. N( 50,8): means- 50, sd- 8, sample is normally distributed. 1sd: 68 % of samples fell in between 1sd away from mean. The resulting units are called standard units. Skewed distribution: samples fell in certain group of intervals, mean will be pulled to the tail of the graphic (not ideal to describe the center) Median: middle number of the average of the two middle numbers if the sample size is even. Symmetric distribution: medium and mean are similar. Skewed distribution: medium and mean are not similar. Quartiles: used to measure spread of a skewed numeric distribution below 1q: 25% below 3q 75%
