data handling and analysis

Created by

isobel howarth

Cards (54)

what is descriptive statistics
describe the data, enabling people to see at a glance and summaries what has been found
what should descriptive statistics enable people to do
people reading your descriptive stats should be able to understand them with no further question necessary
what are the 4 types of descriptive statistics
measures of central tendency (mean, median and mode)
measure of dispersion (range and standard deviation)
graphical representation (bar charts, histograms and tables)
percentages
what is measures of central tendency
the typical or fairly central values
what is the measures of dispersion
to what extent the data is spread out around this central point
what is graphical representations
allows you to eyeball the data really quickly and draw conclusions
what is the mean
the average of all scores
how do you calculate the mean
add up all the numbers in the set of scores and divide by the number of scores that there are
what is the advantage of the mean
the most sensitive measurement as it uses all the scores in a set of data
what is a disadvantage of the mean
can be affected by extreme scores if there is one really small/large scores then this will distort the mean value
what is the median
the central number in a set of scores
how do you calculate the median
rank the values (put them in order of size) then select the score that is in the middle of all the numbers, if there are 2 numbers in the middle then add them together and divide by 2
what is an advantage of the median
not affected by extreme scores so is a good one to use instead of the mean if this is the case
what is a disadvantage of the median
not as sensitive as the mean because not all the scores in a set of data are sued in its calculation and the data is simply ranked and the middle score in the median
what is the mode
simply the most common score in a set of data and is the best for nominal data
how do you calculate the mode
the most used number if data has 2 modes it is said to be bimodal, if more then 2 modes are found it is best to say 'no modal scores'
what is an advantage of the mode
not affected by extreme values so can be used as an alternative to the mean which is affected by extreme values
what is a disadvantage of the mode
not as sensitive as the mean because not all the scores in a set of data are used in its calculation it is simply the most frequently occurring score
what is the measures of dispersion a measure of
how spread out the data is
what is the range
this measures how spread out a set of scores are it is calculated by subtracting the lowest values form the highest
what is an strength of the range
easier to calculate and understand than alternatives for example standard deviation and it is time effective
what is a disadvantage of the range
gives no infomation as to whether scores are clustered around the mean or evenly spread out, unlike the standard deviation and distorted by extreme scores
what is standard deviation
this measure how far on average each score in a set of data is away from the mean
what does a large standard deviation indicate
if a set of scores has a large standard deviation this indicates a wide spread of scores away from the mean (a high variance)
what does a small standard deviation indicate
if a set of scores has a small standard deviation then this indicates that scores are quite close together and clustered around the mean (a low variation)
what is an advantage of standard deviation
all scores are used (unlike the range) therefore it is a much more sensitive measure of dispersion than the range
what is a disadvantage of standard deviation
it is much more time consuming to calculate than the range
what are the 6 things used in a bar chart
each var represents a different category and these are on the horizontal axis (x)
the frequency each category occurs is measured up the vertical axis (y) and is shown by the height of the var
bars should be drawn separately not touching to indicate that each category is sperate and not touching the Y axis
bar charts must indicate an appropriate underlined title which includes the variables on the bar chart
bars need to be accurate so they read the correct values
axis needs to be appropriately labelled and there need to be a key is applicable
how do you write a title for a bar chart
a bar chart to show the ... of ...
be specific
what to histograms have
the vars touch each other which shows that the data is continue rather than discrete
the x-axis is made up of equal-sized intervals of a single category - continuous data
the y-axis represents the frequency within each interval
if there was a zero frequency for one of the intervals the interval remains but without a bar
what does % mean
faction of 100
how do you convert a % to a decimal
remove the % sign and move the decimal point 2 places to the left or divide your % by 100
how can quantitative data be interpreted
when quantitative data has been gathered it can be interpretated by using distribution curves
what is the most common type of distribution
a normal distribution or normal curve and it is often called the bell shaped curve due to it looking like a bell
what are normal distribution
it is symmetrical meaning the distribution and frequency of scores on the left side matches the distribution and frequency if scores on the right side
what do many distribution fall on
a normal curve especially when a large sample of data are considered
what are some examples of a normal distribution
height
weight
IQ
blood pressure
shoe size
what is a normal distribution
the mean, median and mode of a normal distribution are identical and fall exactly in the Centre of the curve
what can some data be
skewed
what does skewed data look like
it tends to have a long tail on one side or the other