When measuring a particular variable in a population (e.g. weight), you would expect a certain amount of variation throughout the population. You could calculate the mean and then use the standard deviation to describe the ‘spread’ of the data away from the mean. You could also plot the data using a histogram to show the frequency distribution of the variable across the population. That histogram will take on a certain ‘shape’ depending on how that particular variable is distributed. A very common shape is one called the ‘normal distribution’. The normal distribution is the classic bell curve. You have already seen various types of distributions on the stattrek website when you looked at patterns in data. You should now read more about the normal distribution and standard deviation here:
You can skip the sections on ‘Standard Scores’ (z-scores) and ‘Why Standardize’.
You should try to answer the 10 questions at the bottom of the page to help you better understand the types of questions you can answer about a population when you know the mean and standard deviation.
You should complete this and the Graphing with Google spreadsheet before class on Tuesday, 3/10/15