1: Basic Concepts Flashcards
what is a nominal scale of measurement (example)?
- numbers or names serve as labels
- but no numerical relationship between values
- e.g. gender, political party, religion
what is a ordinal scale of measurement (example)?
- data is organised by rank
- values represent true numerical relationships
- but intervals between values may not be equal
- e.g. race position, likert scale ratings
what is a interval scale of measurement (example)?
- true numerical relationships and intervals between values are equal
- but scale has not true zero point
- e.g. temperature (ºF), shoe size
what is a ratio scale of measurement (example)?
- true numerical relationships, equal intervals and true zero point
- e.g. height, distance
when should you use a median instead of a mean for a measure of central tendence?
Discrete or continuous data which is not normally distributed
When should you use the mode instead of the mean?
categorical data
what is the measure of spread for the median?
range
define: Mesokurtic
- the curve of distribution is the same as normal distribution
define: Platykurtic
- flatter distribution than normal distribution
define: leptokurtic
- more concentrated distribution than normal distribution
define: bimodal
when there are 2 peaks in the distribution
define: uniform data
when everything is evenly distributed
if there is a positive skew which side is there more data on?
left
if there is a negative skew which side is there more data on?
right
how to calculate a z-score
= (score - pop mean)/ pop standard deviation
what do z-scores tell you?
Z-score indicates how much a given value differs from the standard deviation -think about 1.96
define: sampling distribution
distribution of a statistic across an infinite number of samples (e.g. sampling distribution of the mean) from a population
define: standard error
the standard deviation of the sampling distribution of the mean
how to calculate standard error
standard deviation/ SQRT(sample size)
what is the estimated standard error
sample standard deviation/ SQRT sample size
How do we calculate the 95% CIs around a sample mean?
SDsample mean +/- SD * 1.96
what do t-values show?
represents the distribution of sample mean differences when the null hypothesis is true. We measure the distance between our t-value value and this distribution to help us see if we can reject the null
what is the difference between a t & p value?
t-value is not a probability, and therefore its value is unbounded
what is a p-value?
the probability of measuring a difference of that magnitude if the null hypothesis is true
what is the a (alpha) value?
threshold level of probability where we will be willing to reject the null hypothesis
– In Psychology we typically set α = .05
should p be < or > than a to reject the null
p<a = reject the null
if p ≤ .05 we reject the null
what is a type 1 error?
rejecting the null hypothesis when it is true
what is a type 2 error?
failing to reject the null hypothesis when it is false
