Unit 4

Question 1

What is the purpose of inferential statistics

Answer 1

lets us make conclusions about a larger population based on data from a smaller sample

Question 2

What are 2 tests we can use to test if a variable has a normal distribution

Answer 2

histogram
box plot

Question 3

How many scores on a normal distribution fall above the mean of 0 and below

Answer 3

50%

Question 4

what percentage of scores fall between the mean and one standard deviation above or one standard deviation below

Answer 4

34%

Question 5

what percentage of scores fall between -1 and +1 SD

Answer 5

68%

Question 6

what percentage of scores fall between -2SD and +2SD from the mean

Answer 6

96%

Question 7

Why do distributions of score in the behavioural and social sciences typically follow a normal curve

Answer 7

central limit theorem

Question 8

What is the central limit theorem

Answer 8

if you take many random samples from a population and calculate their means those means will form a bell shaped distribution even if the original population is not normal

it means that sample means behave normally and predicatbaly even when the population does not

matehematical principle that the distribution of the sums (or means) of scores taken at random from any distribution of individuals will tend to form a normal curve

Question 9

what is the empirical rule

Answer 9

68-95-99.7 rule
68% of the scores fall within one standard deviation of the mean
95% of the scores fall within 2 standard deviations of the mean
99.7% of the scores fall within 3 standard deviations of the mean

Question 10

what pecentage of scores on a normal curve are between 1 and 2 SD above the mean

Answer 10

14%

Question 11

what is the percentage of scores between +/-2 SD and +/-3 SD

Answer 11

2%

Question 12

why are true random samples difficult to obtain

Answer 12

it is impossible to obtain a complete list of a population
not everybody selected agrees to participate
can be costly to track everyone down

Question 13

what is a biased sample

Answer 13

when one or more parts of the population are favored over others

Question 14

what are two types of biased sampling

Answer 14

convenience
voluntary response

Question 15

What are three types of random sampling techniques

Answer 15

stratified random sample
multistage sampling
simple random sampling

Question 16

what is stratified random sample

Answer 16

random sampling technique
take a random sample divide it into strata of similar people and take a random sample from each strata

Question 17

what is a multistage sample

Answer 17

random sampling technique
go through different stages to find your sample
ex. if you have 3 groups stage one would be picking a agroup. stage 2 would be to d another SRS
could use a random digits table to get your sample

Question 18

what is a simple random sample

Answer 18

each individual has an equal chance of being surveyed

Question 19

what is probability

Answer 19

expected relative frequency of a particular outcome

Question 20

Without using a normal curve table, about what percentage of scores on a normal curve are (a) between the mean and 2 SD above the mean (b) below 1 SD above the mean and (c) above 2 SD below the mean

Answer 20

a. 48%
b. 84%
c. 98%