T - Tests Flashcards
What is the T- Test used for?
Used to determine whether the mean for a sample differs significantly from:
- Estimated population mean (hypothesised mean).
- Mean of another sample drawn from the same population.
What are the two main values used in spirometry?
FEV1 = FORCED EXPIRATORY VOLUME IN ONE SECOND.
Volume of air exhale forcibly from the lungs in one second.
FVC = FORCED VITAL CAPACITY.
Volume of air exhaled from the lungs when you take a breath and blow all the way out.
Explain the key features of a normal distribution.
- Bell - Shaped Curve.
- Mean and Median are equal and located at the centre of the distribution.
- Predictable percentage falls within the 1, 2 or 3 standard deviations of the mean.
What two measurements are used to judge a normal distribution curve?
- Mean
- Standard Deviation
How can you tell something is LESS LIKELY to be normal for that population?
The more standard deviations a value is from the mean.
z = (x-u)/ sigma
Explain this equation.
Z score = single value.
X = Individual Score
U = Test Mean
Sigma = Test Standard Deviation.
What is statistical population?
- Complete set of possible observations.
- Researchers must define the population they are interested in.
What is sample?
Set of observations taken from the population.
What does a good sample allow you to do?
Contains the information that allows you to make conclusions about the population.
What is a parameter?
Value / Characteristic of the whole population.
Usually fixed // maybe unknown or unknowable.
What is a statistic?
Value calculated from sample data. (ie: sample mean).
Value may vary between samples.
Is observable.
What is a point estimate?
Use of a sample statistic to estimate a population parameter.
How do you work out the standard error?
Also known as the standard deviation of sample means
standard deviation / square root of number of samples.
What happens as the n increases?
The standard deviation gets smaller.
What is a one sample test?
When a statistical test can tell whether a sample is different from a population.
What is the normal distribution?
The distribution of a parameter in a population.
What is required to work out the z score?
The population mean and standard deviation.
What is normally unknown / unknowable?
Mean and SD.
What happens in a T - statistic where by the sample size increases?
Distributions get taller and thinner.
When does the t distribution reach normal distribution?
Once the sample size exceeds 30.
What does āvā stand for?
Degrees of freedom.
What is degrees of freedom?
The number of values in the final calculation of a statistic which are free to vary.
How do you work out the degrees of freedom?
Sample Size - 1
