Lecture 2 Flashcards
What does leptokurtic mean?
A “squished” normal distribution. (a high high peak)
What does platykurtic mean?
A “squashed” normal distribution (little to no peak, very spread out)
What doe the standard deviations mean in normal distributions?
1 SD = 68%
2 SD = 95%
3 SD = 99.5%
What is the significance of 1.645 and 1.96?
Two sided versus one sided hypothesis test.
In a two sided test your 5% is split, thus you need a bigger number to reject the null hypothesis (1.96). For a one-sided hypothesis test you need a smaller number to reject the null (1.645)
What does it mean when doing a case control odds ratio, if the odds ratio is not 1 or close to 1?
The two variables are dependent on one another.
How do you calculate the mean of a binomial distribution?
µ (mean) = np
Why/when would you use a Poisson distribution & formula?
If we are interested in the probability of occurrences over a specified period of time, we can use a different form of probability distribution called the Poisson.
Are statistics good at correcting for bias?
No!
What is a stratified sample and how do you achieve it?
A random sample that meets some sort of criteria. e.g. a sample of 100 that is 50% male and 50% female
Achieved by separating your sample before starting and choosing 50 from each.
What is a convenience sample and what is a downside?
Using a particular sample because they are easy to enroll or possess some other characteristic. Can lead to bias.
What is the difference between mu and x bar?
mu = true mean, x bar = sample mean
What is standard error?
variability in the means of samples whereas s refers to variability in the observations of individual subjects in one sample.
= SD / sq root of n
What does the central limit theorem say?
If large random samples are taken from even a non-normally distributed population, x-bar will approach normality.
