Week 10-14 Flashcards by Miss J

Give an example: Nominal level of measurement

Ethnic group- Chinese

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Give an example: Ordinal level of measurement

University grades- pass, credit

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Give an example: Interval/Discrete level of measurement

IQ scores

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Give an example: Ratio/Continuous level of measurement

Height

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Give an example: Categorical Data

Nominal and Ordinal

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Give an example: Continuous data

Interval and Ratio

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Define: Continuous data

is an actual value of the measurement

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Define: Categorical data

is the number of cases that fall into a category

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What are the 3 measures of Central Tendency?

Mean
Median
Mode

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Define: Median

is the score that divides a ordered set of scores into two equal halve

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Define: Mean

the average

Sum of a set of scores, divided by the number of scores

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What are the measures of Variability?

Range
Percentiles and Quartiles
Standard Deviation

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Measures of Variability

Define: Variability

Dispersion or spread of scores

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Define: Range

Difference between the highest and lowest score

highest score - lowest score = range

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Measures of Variability

Define: Percentiles and Quartiles

Percentiles divide data into 100 equal portions
Quartiles divide data into 4 quarters
• Q1=25%,Q2=50%,Q3=75%, Q4=100%

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Measures of variability

Define: Standard Deviation

It is the average difference between any score and the mean

Important because it includes information on all scores

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What is called the Point Estimate?

the mean or median

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What is called the Measure of Variability?

the Standard Deviation or the Inter-quartile range

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What is the purpose of Descriptive Results?

Concerned with organising and summarising information about a collection of actual observations

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Descriptive Results

Name the 3 ways data is described?

1) By measures of central tendency2) By measures of dispersion (variabiltiy)
3) By measures of association

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Descriptive Results

Name the methods of describing data

with:

1) Numbers- percentages, SD, central tendency
2) Tables/Figures- Bar chart, histogram, polygon, scattergram

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Name the 2 Frequency Measures in epidemiology

Incidence

Prevalence

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Define: Incidence

The frequency of new occurrences of disease, condition, or death in a defined population over a period of time

Define: Prevalence

The number of persons in a defined population who have a specified disease or condition at a point in time

(Understanding results- step 1) Name the 2 types of Data results

Categorical and Continuous

(Understanding Results) What are the 4 levels of measurement?

Nominal- categories only Ordinal- categories and ranks Interval or Discrete- categories, ranks and equal intervals between Ratio or Continuous- all of the above, plus a true 0 point

(Understanding results- step 2) What are the 2 types of Results?

Descriptive | Inferential

Define: Inferential Statistics (results)

are about what can be inferred from the sample to the population

Explain the purpose of Inferential Statistics

are necessary for answering questions for those beyond the sample - cause, prevention, diagnosis, treatment, prognosis

How do we estimate Population characteristics from Sample data?

We use the normal curve as a model for making statistical assumptions and estimations

If results are Inferential, the results are about what 2 types of significance?

Statistical significance | Clinical significance

(Hypothesis Testing) Define: Null Hypothesis (Ho)

proposes that there is no effect

(Hypothesis Testing) Define: Alternative Hypothesis (Ha)

the opposite of the null hypothesis

Define: Hypothesis Testing

the process of deciding statistically whether the findings of an investigation reflect chance or "real" effects at a given level of probability

What are the 2 possible explanations for a positive outcome in a study?

1. that the research hypothesis is correct | 2. that the observed difference between groups occurred by chance

Define: Probability

is the likelihood an event will occur, given all possible outcomes

Define: p-value

probability due to chance | p=0.05

Explain: Statistical Significance (inferential results)

- hypothesis testing - result is a probability value (p-value= 0.05) - results are statistically significant if they are below 0.05

Explain: Clinical Significance (inferential results)

- provides an estimate we can use in real practice - result is a confidence interval - results must be above the MID to be clinically significant

Define: Point Estimate

a single number regarded as the most plausible value from the sample data

Explain: Estimation

will provide a result AND a degree of certainty

Define: Measure of Variability

turns the sample result (point estimate) into what we estimate for the whole population

What is the most important statistic to find in a results section?

measure of variability- what we estimate for the whole population

What is the common measure of variability used for estimation?

the Confidence Interval

Explain: Confidence interval

- the 95% suggests the degree of certainty of the estimation

Define: Minimal Important Difference (MID)

is the smallest worthwhile difference expected by a patient to proceed with the treatment

What is Clinical Significance?

is when the treatment effect (confidence interval) is equal or more than the MID

Define: Risk ratio

is a comparison of risks

What are the Difference Values in Continuous and Categorical data?

Continuous: difference value=0 Categorical: difference value=1

A result is clinically significant if...

- the point estimate is larger than the MID - most of the confidence interval is larger than the MID - a narrow confidence interval (narrow=precise)

(Tree/Forest Plots) When is 0 used as the point of no effect?

when data isn't a ratio

(Tree/Forest Plots) When is 1 used as the point of no effect?

when data is a ratio

Explain with an example: Cohort Study

Prospective: Pick people who smoke and people who don't smoke Follow participants over time- see who gets lung cancer

Explain with an example: Case-Control Study

Retrospective: Pick cases of people who already have lung cancer and people who don’t Go back in time and find out who smoked

When is a result statistically significant?

when the p-value of the results are below p=0.05

Define: Measures of Central Tendency

These are numerical indices that provide a quantitative summary of the centre of the distribution (Mean, mode and median)