Statistics Flashcards
What is the population?
The entire group of individuals is called the population
What is a sample?
A sample is a group selected to represent the population in a research study e.g. population is too large to examine all
What is a variable?
A characteristic that can change or take on different values e.g. height, gender
What are the two main types of data?
Categorical (Qualitative)
Numerical (Quantitative)
What are two types of Qualitative data?
Nominal- no particular order e.g. Hair colour
Ordinal- some order e.g. pain threshold
What are the two main types of Quantitative data?
• Discrete - data that consist of indivisible categories/fixed numbers. e.g., number of
teeth, number of children in a family
• Continuous - infinitely divisible into whatever units a researcher may choose, e.g. weight
What are two types of continuous data?
Interval- no.s with known differences between variables, e.g. time
Ratio- no.s that have measurable intervals where difference can be determined, such as height or weight
What are the 3 measures of central tendency?
Mean
Median
Mode
What are three measures of dispersion?
Range
Interquartile range
Standard deviation
What does the mean represent?
Average or arithmetic mean of the data
What does the median represent?
The middle value when the scores are ranked in order
What does the mode represent?
Most often occurring value
What does the range represent?
Highest to lowest values; this fails to give an indication of the spread of observations about the mean.
What does the Interquartile range represent?
Values that capture the middle 50% of the
distribution. The upper and lower quartiles are the 75th and 25th percentiles.
What does the standard deviation represent?
How closely do values cluster around the mean value in a normally distributed population. It describes the spread of observations on either side of the mean.
What is meant by the standard error of the mean?
The standard deviation of a number of means from different samples of the same population.
This gives an indication of the precision of the sample mean as an estimate of the population mean
What is the difference between the standard deviation and the standard error?
Standard deviation shows how individuals within the sample differ from the mean of the sample.
Standard error is an indication of how far the mean of the sample is likely to be from the actual target population mean.
What are confidence intervals?
A way to indicate the probability that the mean for a population lies within a range of values.
The width of the confidence interval indicates the precision of the estimate.
Why is normal distribution important?
Because parametric statistics assume normal
distributions
How can we tell if a variable is normally distributed?
Distribution unlikely to be normal if:
• Mean is very different from the median
• Two SDs below the mean gives an impossible answer (e.g. height <0 cm)
What is the difference between parametric and non-parametric tests?
Parametric tests assume that data are normally distributed.
Whereas, Non-parametric tests make fewer assumptions about the data.
What is the difference between independent and paired samples?
Independent or unpaired data refers to data from two groups with different members.
Paired samples are samples in which natural or matched couplings occur.
Explain what is meant by the null hypothesis?
When we say the difference in observations between two groups is purely due to chance.
When the results of an investigation are not likely due to chance alone; the null hypothesis may be rejected in favour of the alternative hypothesis.
What is a two-tailed test?
A two-tailed test exists where we do not have a direction of difference between groups for the alternative hypothesis
i.e. the results are different but we cannot say if they are better or worse.
