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Medicine Phase 1 mine > Critical numbers > Flashcards

Critical numbers Flashcards

1
Q

What is a sample?

A

A selection from a population which aims to represent the whole population.

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2
Q

Name some types of bias and explain

A

Sampling bias, some people are more likely to be included in your sample than others. (omission, inclusive bias)
Recall bias, people cannot remember information correctly
Social- desirability bias, change answers to more acceptable ones
Information bias, errors in your measurements.

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3
Q

What is a confounding factor?

A

something that is related to the outcome and the characteristic of interest

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4
Q

What are the categories of studies?

A

– Experimental vs. Observational
– Retrospective vs. Prospective
– Individual vs. Population level

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5
Q

What is an experimental research method?

A

One where the researcher has made some kind of intervention eg crossover trial or RCT

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6
Q

What is an observational study?

A

There is no intervention data is just collected about what happens, E.g. case-control, cross-sectional,cohort,ecological studies

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7
Q

What is a retrospective study?

A

One which looks back at what has already happened case-control

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8
Q

What is a prospective study?

A

Collect information then follow up over time Cohort study

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9
Q

What is an individual study?

A

Collect information about individuals all studies except ecological.

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10
Q

What is a popilation study?

A

Talk about a whole population

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11
Q

What is the ecological fallacy

A

making inferences from populations about an individual.

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12
Q

Describe case-control studies

A

Find individuals with the outcome and a similar group without and take a random sample of each and see who had the eposure compared to others.

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13
Q

What are the strengths and weaknesses of case-control studies?

A

Strengths- good for rare diseases as sample can be focussed, quick results as its retrospective, can look at multiple causes, it is inexpensive.
Weaknesses- subject to recall bias, can’t prove causality, prone to selection and information bias, hard to choose controls, incidence of disease cannot be calculated

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14
Q

Describe a cross-sectional study

A

takes a snapshot of what is happening at the current time

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15
Q

What are the strengths and weaknesses of a cross-sectional study?

A

Strengths- quick to do, relatively cheap to generate hypotheses, few eithical problems
Weaknesses- could be a medical oddity, prone to sampling bisas no time reference

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16
Q

Describe a cohort study

A

Collect information on a sample and follow- up over time to explore who gets the outcome

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17
Q

What are the strengths and weaknesses of a cohort study?

A

They distiguich anecedent causes from concurrent associated factors. can calculate relative and absolute risks. can look at many outcomes or exposures less chance of bias as measured before disease onset/
Weaknesses- cannot be certain of causation, long study periods, follow up can be a problem, diagnosis of disease may change over time.

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18
Q

Describe a RCT?

A

Have multitple groups with different exposures compare the outcomes to get a causal relationship.

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19
Q

What are the strengths and weaknesses of an RCT?

A

Strengths- should equalise confounding factor effects, randomly allocating reduces bias blindign can be used, significance tests are better, the confounders and mabiases are minimised
Weaknesses need a big enough sample to show it works, volunteer bias can be a problem, ethical issues can be a problem for studies and poor compliance can lead to loss in power of the study.

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20
Q

What is a crossover trial?

A

an extension to an RCT. everyone does all the arms of the study. which reduces confounding even more as each person can be compared across the arms. thre can be carry-over effects and more technical analyses

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21
Q

What steps should be taken in an RCT to minimise bias?

A

Blinding, randomisation, placebos, matching

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22
Q

What are the two main groupings for variables?

A

Categoric and numeric

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23
Q

What are the types of categoric variables?

A

Binary, ordinal, nominal

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24
Q

what are the numeric variables?

A

Discrete and continuous

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25
Q

What is the odds?

A

number with the outcome/ number without the outcome

26
Q

How can you quantify differences?

A

Risk differences, risk ratio and risk difference

27
Q

What is risk difference?

A

the difference between the two risks you have calculated

28
Q

What is a risk ratio?

A

divide one risk by the other. the top group is the focus group compared to the other one.

29
Q

How do you interpret a risk ratio?

A

RR> 1 the focus risk is higher
RR=1 the two groups are the same
RR<1 the focus risk is lower than the other
1 is no difference

30
Q

How can you swap the focus of the risk ratio is?

A

inverse 1 divide by it

31
Q

What is odds ratio?

A

Odds divided by odds

32
Q

How do you interpret odds ratio?

A

OR> 1 the focus risk is higher
OR=1 the two groups are the same
OR<1 the focus risk is lower than the other
1 is no difference

33
Q

Why might you use risk ratio?

A

It puts it in context more

34
Q

Why do we use Odds ratios?

A

they are useful for some statistical methods

35
Q

If something is very rare how does OR and RR compare?

A

RRroughly= to OR for rare outcoumes

36
Q

If something is more prevalent what happens to RR and OR?

A

RR<

37
Q

What is the median

A

middle value in sequential order

38
Q

What is positive skew?

A

where the peak is to the low end most of the values are in the lower end, the mean is greater than the median

39
Q

What is negative skew?

A

most of the values are to the right, the mean is less than the median

40
Q

How to decide which measure of spread to use?

A

if it is symmetric then use mean and SD otherwise use median and IQR as they are less affected by skew

41
Q

What is the use of the normal distribution?

A

The sd can tell you about percentage certainty

42
Q

What are the limits of correlation coeffiecient?

A

-1 perfect negative correlation 0 and +1

43
Q

What is standard error?

A

How well your sample representing the population.

44
Q

How can standard error be reduced?

A

Enlarging the sample size the more similar the people are.

45
Q

What is the formula for the standard error of a mean?

A

SD/root(n)

46
Q

What is the difference between standard error and standard deviation?

A

Standard deviation is a descriptive value about the data collected while standard error is an inferential number about how well our estimate represents the true population value

47
Q

What is the use of confidence interval?

A

It is often used as a comparative value between data sets. can be used for inferential statistics

48
Q

What are confidence intervals?

A

The true value is quite certain to lie between those two points.

49
Q

What are confidence interval calculated from?

A

Standard error and SD values

50
Q

What is the null hypothesis?

A

There is no link between the two variables

51
Q

What is a p value?

A

Probability that the mean could be from the standard deviation.

52
Q

If mean is close to the null what will the p value be?

A

Close to one

53
Q

How should you phrase rejecting the null hypothesis?

A

The evidence suggests to reject the null hypothesis

54
Q

What is the generally accepted significant p value?

A

p=0.05 for statistical significance

55
Q

What is another significance test?

A

One sample t test, two sample t test, chisquare tests, ANOVA test, Pearson correlation coefficient

56
Q

What is regression?

A

Plotting the correlation between variables using y=a+bx

57
Q

What is the effect of using multivariable method?

A

It accounts for the effect of confounding factors

58
Q

How can you appraise study design?

A

Who is sturied? are there missing groups over sampling? is it clear what the aim is

59
Q

What can you appraise the descriptive statistics?

A

Summariesed data appropriately, Normal distribution, SD

60
Q

What can you appraise the inferential statistics?

A

p values CI did they look at normality test

Medicine Phase 1 mine (21 decks)

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