part 3 Flashcards
maths
what are measures of central tendency used to give?
they are averages which give he information about the most typical values in a set of data
how do you calculate the mean?
add all the values together and divide by the number of scores
evaluate the use of the mean
strength
- the most sensitive of al measures because it takes all scores into account
limitation
- can be easily distorted by extreme values
how do you calculate the median?
place in order of low to high and find the middle value
if there’s an even number, find the number in between both values
evaluate the use of the median
strength
- extreme scores do not effect it and will not distort and very easy to calculate
limitation
- less sensitive than the mean as it doesn’t include all of the scores
how do you calculate the mode
the most frequently occurring number
- may be bi-modal meaning there’s 2 modes or multi-modal meaning there’s more than two modes
evaluate the use of the mode
strength
- easily calculated
limitation
- crude measure and should be avoided if possible but it can be the only measure that can be used if it’s categories
what are measures of dispersion?
based on the spread of scores and tell us how far scores are spread from each other
how do you calculate the range?
largest value - smallest value
what is shown if the mean value for two sets of scores is the same but the range is different?
the set of values which has the higher value for range shows the scores are more widely spread (more dispersed)
evaluate the use of the range
strength-
easy to calculate
limitation
only takes into account the two extreme values so may be unrepresentative of the data as a whole
what is standard deviation?
a more precise measure of dispersion and tells us how the mean scores are spread around the mean
what is a low standard deviation showing?
the data are tightly clustered around the mean
what does a high standard deviation show?
the scores are widely spread and not all the pps were affected in the same way
how do you distinguish between a low and high standard deviation?
the larger the standard deviation score, the more widely dispersed from the mean
evaluate standard deviation
strenth
- more sophisticated than the range
limitation
- can be distorted by an extreme score
what are bar charts used for?
plotting discrete (discontinuous) data which means they do not overlap in any way
==> for exaple, breeds of dogs or what newspapers you read
what are histogram used for?
the x-axis doesn’t show discrete data aa it is continuous and there are no gaps between the bars
what are line graphs used for
to show change over time or trials
what are scattergraphs used for?
shows the relationship between two variables
what do normal distributions curves show? (key features)
- mean, median and mode are all at the exact same midpoint
2- scores are symmetrical from the midpoint - the dispersion of scores on either side of the mid point is consistent ad expressed as standard deviations
what does a skewed distribution curve show?
data is not symmetrical and the data clusters towards one end
on a skewed distribution curve, what central tendency is always at the peak?
mode
what is a left-skewed distribution?
tail is to the left meaning most of the data is towards the right.
- this is due to the mean being affected by extreme scores and so gets dragged to the left
what is a right-skewed distribution?
tail is to the right meaning most of the data is towards the left.
- this is due to the mean being affected by extreme scores and so gets dragged to the right
is the mean value greater in a left or right skewed distribution?
right-skewed
