Test 2

Question 1

What is a normal distribution?

Answer 1

A theoretical distribution of values, also called bell curve

Question 2

Why is a normal distribution theoretical?

Answer 2

because its frequency distribution is derived from a mathematical formula and not the observations of real data

Question 3

What are some features of a normal distrbution?

Answer 3

the left and right tails continue to infinity and do not touch x axis, its unimodal and symmetrical

Question 4

Why are normal distributions important?

Answer 4

many variables are thought to be noramlly distributed in the population (height, IQ), most inferential statistics assume normality, you can determine the proportion of scores in a normal distribution that are associated with any given score

Question 5

What is the standard normal distribtuion?

Answer 5

aka z distribution, normal distribution of z scores, same features of normal distribution but mean is 0 and std is 1

Question 6

What is the difference between standard normal distributions and normal distributions?

Answer 6

standard normal is distribution of z scores and normal is distribution of any scores

Question 7

What is the 68-95-99.7 rule?

Answer 7

in a normal distribution, 68% of scores fall within 1 std, 95 within 2, and 99.7 within 3

Question 8

If you wanted to find the z score in a standard normal distribution that separates the top 10 percent from the rest, how would you?

Answer 8

find 0.1000 in the column for proportion of tail or 0.9000 in column for proportion in body, look at corresonding z score

Question 9

What are the two requirements for a random sample?

Answer 9

each individual has an equal chance of being selected, and if more than one individual is selected, the probabilities must stay constant for all selections

Question 10

What is sampling with replacement?

Answer 10

when a subject is picked they are put back into the population before they pick again

Question 11

what are the four steps of hypothesis testing?

Answer 11

state hypothesis and alpha level, lcoate the critical region, compute the test statistic, make a decision

Question 12

How do you find the standard error of M?

Answer 12

std/sqrt of n

Question 13

How do you find z value using standard distribution of mean?

Answer 13

z = M - m/std/sqrt of n

Question 14

How would you find the probability of a z score falling between 0.5 and 1?

Answer 14

find proportion of body for 0.5 and subtract proportion of tail for 1

Question 15

What is a type 1 error?

Answer 15

rejecting the null hypothesis when you shouldn’t (it was true but still got rejected)

Question 16

What is a type 2 error?

Answer 16

failing to reject the null hypothesis when you should

Question 17

How does increasing the alpha level from 0.01 to 0.05 affect the power of hypothesis?

Answer 17

increases it

Question 18

How does changing from a 1 tailed test to a 2 tailed test change the power of the hypothesis?

Answer 18

decreases power if the effect is in the predicted direction

Question 19

If p is less than a we ?

Answer 19

reject the null

Question 20

If p is greater than or equal to a we ?

Answer 20

fail to reject the null

Question 21

When is a t statistic used instead of a z statistic used in a hypothesis test?

Answer 21

when population standard deviation is unknown

it uses the sample deviation or variane instead

Question 22

Why are t distributions flatter and more spread out than normal distributions?

Answer 22

because they are more variable since we do not know the population variance

Question 23

What is an independent measures study?

Answer 23

uses a separate sample for each of the treatments or populations being
compared

Question 24

How do you calculate the pooled variance given SS= 1740 and SS= 1620, and n=15?

Answer 24

1. find sample variance for each
   - s^2 = 1740/15-1 =124.29
   - s^2 = 1620/15-1 = 115.71
2. find the pooled variance
   s^2 x df + s^2 x df/ n + n -2
   (124.29 x 14) + (115.71 x 14) / 15 + 15 - 2

Question 25

What formula can be used to calculate the estimated standard error for the sample mean difference?

Answer 25

SEdiff = sqrt(pooled variance/n + pooled variance/n)

Question 26

What is the formula for sample variance?

Answer 26

s^2 = SS/n-1

Question 27

What are non parametric tests?

Answer 27

make few if any assumptions about the populations from which the data are
obtained, any scale of measurement is acceptable

Question 28

How to calculate expected frequencies?

Answer 28

multiply the two together and divide by n

Question 29

What is the difference between the chi square goodness of fit test and the test for independence?

Answer 29

goodness of fit addresses only one nominal variable, independence addressses two nominal variables

Question 30

What are some examples of parametric tests?

Answer 30

pearsons correlation, one sample t test

Question 31

What are some examples of non parametric tests?

Answer 31

chi square, spearmann rank correlation

Question 32

How do you calculate degrees of freedom for a pearson correlation test?

Answer 32

df = n - 2

Question 33

How do you calculate r for pearson correlation?

Answer 33

r = SP/ sqrt(SSxSSy)

Question 34

WHat does SP mean in r formula?

Answer 34

measures how x and y covary, equal to the summation of (X-Mx) x (Y - My)

Question 35

How do you find SSx and SSY in r formula?

Answer 35

SSx is summation of squared deviations (X-Mx) SSy is same but for Y variable and My

Question 36

When do you use pearson correlation?

Answer 36

linear relationship, both variables are interval/ratio