lecture 3 - data distributions and probability

Question 1

what is a normal distribution?

Answer 1

if a continuous (ratio-interval) random variable has a symmetric bell-shape curve, it is considered to have a normal distribution

Question 2

what is the standard deviation and what % lies within each standard deviation?

Answer 2

• Measure of variation of data
  ○ Approx. 68% within 1 SD
  ○ Approx. 95% within 2 SD
  ○ Approx. 99% within 3 SD

Question 3

what is the mean of different samples known as

Answer 3

sample means

Question 4

what is the central limit theorem

Answer 4

sample of size n selected from a population will have:
- approximately normally distributed means
- means of sample means = population mean

if population was normally distributed + good sample size: mean of sample means = population mean and will also be normally distributed

Question 5

what is negative skew?

Answer 5

negative direction of skew

Question 6

what is positive skew?

Answer 6

positive direction of skew

Question 7

what is the distribution of sample means?

Answer 7

• the distribution of infinite number of sample means from a population will be approximately normal
  ○ If the sample size is large or if the population is normally distributed
  AND the observations is in the sample are independent
  AND it looks the same as the normal distribution for individuals within a group

Question 8

what is the z-score equation?

Answer 8

Z = x - mean/standard deviation

Question 9

what is a t-test?

Answer 9

seeing what the difference is between the 2 groups