Week Five - Statistical Hypothesis Testing Flashcards
What do standardised scores help do?
Determine how extreme/unusual a score is and to compare data from different scales.
Z-scores =
M = 0, SD = 1
Method for converting raw scores to Z-scores
Subtract mean from individual score
Divide by standard deviation
𝑧 = 𝑥 − 𝑥 /SD
Z scores allow what?
Comparison on different scales
What is SD?
A quantity expressing by how much the members of a group differ from the mean value for the group.
M ± SD describes
the distribution of a sample.
For a normally distributed sample, M ± SD contains what percent of observed scores?
~68%
Does sample size affect SD?
No. Size of the sample does not systematically affect SD.
What is a SE?
The standard error is a statistical term that measures the accuracy with which a sample distribution represents a population by using standard deviation.
In statistics, a sample mean deviates from the actual mean of a population—this deviation is the standard error of the mean.
Measures how far the sample mean of the data is likely to be from the true population mean.
What does a SE describe?
The variability of statistics and the expected distribution of statistics if sampling was repeated many times.
Does sample size affect SE? What is the relationship?
SE is systematically affected by sample size
Inverse relationship
Bigger samples have smaller SE.
What is a confidence interval?
A confidence interval is a range statistic. It provides a range within which we have a specified level of confidence that the true population value lies
95% CIs are the likely range within which the true value of the population parameter sits.
Narrow 95% CIs indicate … while Wide 95% CIs indicate
high precision.
low precision.
Can CI’s be used to describe sample distribution?
CIs cannot and must not be used to describe sample distribution.
What should you use to describe the distribution of your sample?
Use SD if you want to describe the distribution of your sample.
What is a p-value?
A p-value is the probability that a sample statistic as extreme or more extreme than the observed sample would occur if random variation is the only cause of variability.
What p-value means statistical significance
What is a Null Hypothesis?
When we assume the size of the observed effect is purely a result of random sampling (no, or nil effect).
What is the alternative hypothesis?
The hypothesis you hope to support.
Can be directional (one-tailed).
Can be non-directional (two-tailed).
When P =
Reject the null hypothesis and accept the alternative hypothesis.
A p-value = >.05 means what?
A statistic as large or larger would occur more than 5% of the time IF only random sampling is responsible for the variation.
when a p-value = >.05 we do what?
Fail to reject the null hypothesis.
What is a Type I error?
False positive
A type 1 error occurs when a researcher incorrectly rejects a true null hypothesis. This means that your report that your findings are significant when in fact they have occurred by chance.
What is a Type II error?
False negative
A type II error occurs when a researcher fails to reject a null hypothesis which is really false. Here a researcher concludes there is not a significant effect, when actually there really is.
