Module 2

Question 1

What value do probabilites have to be between?

Answer 1

• 0 and 1
• 0 and 100%
• 10:1

Question 2

What does a probability of 1 mean?

Answer 2

• the event is certain to occur

Question 3

What does a probability of 0 mean?

Answer 3

• the event is certain not to occur

Question 4

What is the probability distribution?

Answer 4

• describes the probability of every event

- applies to both categorical and continuous data

Question 5

What must the total area under a normal curve equal?

Answer 5

• 1 or 100%

Question 6

What is standard normal distribution?

Answer 6

• normal distribution with mean = 0 and sd = 1

Question 7

What happens to the normal distribution curve when the mean increases?

Answer 7

• moves across the x axis indicating a higher mean

Question 8

What happens to the normal distribution curve when the sd decreases?

Answer 8

• the distribution becomes skinnier implying a smaller range in values

Question 9

What are the nice rules for conversion of normal distribution?

Answer 9

• 68% of values are within 1 sd of mean
• 95% of values are within 2 sd of mean
• 99.6% of values are within 3 sd of mean

Question 10

What is statistical inference?

Answer 10

• make inferences about population based on data from sample

Question 11

What is sampling variability?

Answer 11

• variation in results from different/random samples of the same population

Question 12

To make an inference about the population does the sample need to be representative?

Answer 12

• yes

Question 13

What happens to a histogram when the sample size increases?

Answer 13

• becomes narrower
• mean becomes less susceptible to single values
• sd decreases

Question 14

What is standard error (se)?

Answer 14

• standard deviation of the sample means

- measures amount of variability in the sample mean

Question 15

What happens to standard error as the sample size increases?

Answer 15

• decreases

Question 16

What is the se equation?

Answer 16

se= standard deviation of sample/ square root (size of sample)

Question 17

What is standard deviation

Answer 17

• measures amount of variability in sample

Question 18

What is the central limit theorem?

Answer 18

• if raw data is not normally distributed, means of samples taken from the distribution will be normally distributed

Question 19

What should results be reported with?

Answer 19

• caveat

e. g. based on a study og 1000 mothers from Brisbane

Question 20

Is it easier to prove or disprove a hypothesis?

Answer 20

• easier to find evidence against a hypothesis

Question 21

What is a Null Hypothesis (H0)?

Answer 21

• nothing is happening

e. g. the new drug doesn’t change blood pressure

Question 22

What is an alternative hypothesis (H1 or Ha)?

Answer 22

• something is happening

e. g. the new drug changes blood pressure

Question 23

What is a one-tailed hypothesis?

Answer 23

• has a direction

e. g. new drug lowers blood pressure

Question 24

What is a two-tailed hypothesis?

Answer 24

• doesn’t have a direction, just a change (could be positive or negative)
  e. g. new drug changes blood pressure

Question 25

What type of hypothesis does research questions have?

Answer 25

- alternative

Question 26

What are the 6 steps to hypothesis testing?

Answer 26

1. state null and alternative hypothesis 2. collect data 3. summarise data appropriately 4. what would data look like if the null hypothesis was true 5. calculate discrepancy between groups 6. make decision and conclusion

Question 27

What is test statistic?

Answer 27

- discrepancy between the data and what is expected under the null hypothesis

Question 28

what is the equation for test statistic?

Answer 28

(observed-expected)/precision

Question 29

How do you calculate an overall estimate of se using both samples?

Answer 29

= square root (se1 squared + se2 squared)

Question 30

How does the value of the test statistic determine?

Answer 30

the p-value and ultimatelt whether the difference is statistically significant

Question 31

What is the p-value/significant level?

Answer 31

- probability of observing the data if the null hypothesis is true - lower p-value indicate the null hypothesis is less plausible

Question 32

What p-value is said to make results statistically significant?

Answer 32

5% or <0.05

Question 33

What is a true positive?

Answer 33

- rejected null hypothesis and shown true effect of H0 is not true e. g. guilty in jail

Question 34

What is a type 2 error/false negative?

Answer 34

- the null hypothesis is not rejected but it is not really true - <0.2 e. g. guilt but no jail

Question 35

What is a type 1 error/false positive?

Answer 35

- the null hypothesis is rejected but there is evidence it has a true effect - <0.05 e. g. not guilty in jail

Question 36

What is the power equation?

Answer 36

= 1 - type 2 error

Question 37

What is a confidence interval (Cls)?

Answer 37

- specify boundaries within which we believe the population values will fall

Question 38

What is the equation for 95% Cl for the mean?

Answer 38

= mean + or - 1.96xse | interpretation: there is a 95% probability that this interval contains the true population mean

Question 39

What is 99% of the standard normal distribution within?

Answer 39

-2.58 to 2.58 se of the mean

Question 40

What is 95% of the standard normal distribution within?

Answer 40

-1.96 to 1.96 se of the mean

Question 41

What p-value determines when the Cl must be reported?

Answer 41

p<0.05

Question 42

What hypothesis does the p-value tell you about the likelihood of?

Answer 42

null hypothesis