week 5 Flashcards
Why do we use statistics
As real data is very messy as there is data for different conditions and different groups
what are measures of central tendency’s
the middle point of a frequency
we cannot draw any inferences or generalisations
types of measures of central tendency’s
the mean
the median
the mode
what is the weakest and strongest type of data
weakest: categorical: nominal then ordinal
Strongest: continuous: interval then ratio
What types of central tendency can be used with certain types of data
Nominal only mode
ordinal: median, ordinal
Interval: mean, median and mode
Ratio: mean, median and mode
What is mean
most commonly used
symbol is ether an x or m
uses all the data set
How do you calculate mean
Add up all the values/scores and divide by the number of values /score
What is the median
it is simply the middle value
How do we calculate the median
Odd number: place the data in order from lowest to highest, follow the equation above, take the total number of participants and ass 1, then divide this value by 2, this gives us our median position
Even data set: place even data in order, use the same equation calculate the middle position of data set. Take the the value for the position before and after and then add them up and divide them by 2
What is the mode
the value which appears most frequently in the data set
Bimodal- have two modes
Multimodal- have more than two modes
What is measure of dispersion
how much the data vary
What are the types of measure of dispersion
the range
minima and maxima
variance
standard deviation
only calculated on continuous data
What is minima and maxima
minima is lowest values in the data maximum is the highest value
What is the range
the highest value in the data set minus the lowest and then add one
What is variance
amount of spread
calculated by examining the degree to which a persons score/ data point differs from the group mean
Calculated by identifying how each sore deviates form the mean
What is the equation for variance
S2= the sum of the difference squared/ number of participants-1
What is the steps of calculating variance
calculated the mean
calculate the amount each score varies form the mean
add up all the differences-this value is then used in the equation
complete the equation
What is standard deviation
tells you how well the mean represents the data
When reporting a mean you should also report the standard deviation
What is the equation to calculate standard deviation
Sd= the square root: the sum of the difference squared/number of participants-1
What is normal distribution
Referred to as the bell curve
the mean, median and mode are all the same
68% probability of selecting a score between +1 and -1
95% probability of selecting a score between +2 and -2
What is confidence intervals
typically you’ll see 95% confidence intervals
How to calculating confidence intervals
take the standard error and multiply this by 1.96
Add this to the mean to calculate the upper CI
subtract this from the mean to calculate the lower CI
What is standard error
Quantifies the variability between samples drawn from the same population. It assesses how far a sample statistic likely falls from a population
What is skew
positive- scores go towards the lower scores
Negative- scores go towards the higher scores
Data is skew if value is above 1 or -1
What is Kurtosis
describes the pointyness of a distribution
when the distribution is flat and short it is platykurtic
when the distribution is thin and tall it is leptokurtic
