Stats

I took Statistics 240 in the Fall 2017 semester.  I remember that a normal distribution, or bell curve, is a representation of data around a mean.  68% of data falls within one standard deviation of the mean, 95% within two, and 99% within three.  A chi squared test is used to see if two variables are related. The null is that they are not, but if the p value comes to less than 0.05, then we reject the null and say that the variables are related.  Sampling distributions are used to draw conclusions about an entire population based on data taken from a small subset. When this is done, confidence intervals can be made - generally 95% or 99%. For example, a 95% confidence interval would mean that researchers are 95% confident that the true mean of the entire population lies within the range they set.  When probabilities of events occuring are known and we want to know the probability of something happening based on that repeated event, we use p, the population proportion. We can construct a confidence interval for a population proportion using “p hat.” Z scores are used to test how likely an event is to occur. If a z-score gives us a standard deviation that is not near zero (above 3, for example) we can say that we do not believe the event occurred because the probability is so low.