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PUB561 > Module 2 > Flashcards

Module 2 Flashcards

1
Q

What value do probabilites have to be between?

A
  • 0 and 1
  • 0 and 100%
  • 10:1
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2
Q

What does a probability of 1 mean?

A
  • the event is certain to occur
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3
Q

What does a probability of 0 mean?

A
  • the event is certain not to occur
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4
Q

What is the probability distribution?

A
  • describes the probability of every event

- applies to both categorical and continuous data

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5
Q

What must the total area under a normal curve equal?

A
  • 1 or 100%
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6
Q

What is standard normal distribution?

A
  • normal distribution with mean = 0 and sd = 1
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7
Q

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

A
  • moves across the x axis indicating a higher mean
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8
Q

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

A
  • the distribution becomes skinnier implying a smaller range in values
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9
Q

What are the nice rules for conversion of normal distribution?

A
  • 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
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10
Q

What is statistical inference?

A
  • make inferences about population based on data from sample
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11
Q

What is sampling variability?

A
  • variation in results from different/random samples of the same population
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12
Q

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

A
  • yes
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13
Q

What happens to a histogram when the sample size increases?

A
  • becomes narrower
  • mean becomes less susceptible to single values
  • sd decreases
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14
Q

What is standard error (se)?

A
  • standard deviation of the sample means

- measures amount of variability in the sample mean

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15
Q

What happens to standard error as the sample size increases?

A
  • decreases
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16
Q

What is the se equation?

A

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

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17
Q

What is standard deviation

A
  • measures amount of variability in sample
18
Q

What is the central limit theorem?

A
  • if raw data is not normally distributed, means of samples taken from the distribution will be normally distributed
19
Q

What should results be reported with?

A
  • caveat

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

20
Q

Is it easier to prove or disprove a hypothesis?

A
  • easier to find evidence against a hypothesis
21
Q

What is a Null Hypothesis (H0)?

A
  • nothing is happening

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

22
Q

What is an alternative hypothesis (H1 or Ha)?

A
  • something is happening

e. g. the new drug changes blood pressure

23
Q

What is a one-tailed hypothesis?

A
  • has a direction

e. g. new drug lowers blood pressure

24
Q

What is a two-tailed hypothesis?

A
  • doesn’t have a direction, just a change (could be positive or negative)
    e. g. new drug changes blood pressure
25
Q

What type of hypothesis does research questions have?

A
  • alternative
26
Q

What are the 6 steps to hypothesis testing?

A
  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
27
Q

What is test statistic?

A
  • discrepancy between the data and what is expected under the null hypothesis
28
Q

what is the equation for test statistic?

A

(observed-expected)/precision

29
Q

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

A

= square root (se1 squared + se2 squared)

30
Q

How does the value of the test statistic determine?

A

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

31
Q

What is the p-value/significant level?

A
  • probability of observing the data if the null hypothesis is true
  • lower p-value indicate the null hypothesis is less plausible
32
Q

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

A

5% or <0.05

33
Q

What is a true positive?

A
  • rejected null hypothesis and shown true effect of H0 is not true
    e. g. guilty in jail
34
Q

What is a type 2 error/false negative?

A
  • the null hypothesis is not rejected but it is not really true
  • <0.2
    e. g. guilt but no jail
35
Q

What is a type 1 error/false positive?

A
  • the null hypothesis is rejected but there is evidence it has a true effect
  • <0.05
    e. g. not guilty in jail
36
Q

What is the power equation?

A

= 1 - type 2 error

37
Q

What is a confidence interval (Cls)?

A
  • specify boundaries within which we believe the population values will fall
38
Q

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

A

= mean + or - 1.96xse

interpretation: there is a 95% probability that this interval contains the true population mean

39
Q

What is 99% of the standard normal distribution within?

A

-2.58 to 2.58 se of the mean

40
Q

What is 95% of the standard normal distribution within?

A

-1.96 to 1.96 se of the mean

41
Q

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

A

p<0.05

42
Q

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

A

null hypothesis

PUB561 (3 decks)

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