Measures

• what is a percentage?


  a fraction of 100
• how do you calculate a percentage?


  minority/ total x 100
• how do you convert a percentage to a decimal?


  Divide by 100
• what does standard deviation measure?


  how far on average each score in a set of data is away from the mean
• what are the two measures of dispersion?


  the range and standard deviation
• what does it mean if a set of data has a large standard deviation?


  there is a wide spread of scores away from the mean (a high variance)
• what does it mean if a set of data has a small standard deviation?


  the scores are quite close together and clustered around the mean ( a low variance)
• what is an advantage of standard deviation?


  all scores are used so it's a more sensitive measure of dispersion than the range
• what is a disadvantage of standard deviation?


  it's more time consuming than the range
• what does the range measure?

  how spread out a set of scores are
• how is the range calculated?


  subtracting the lowest value from the highest value
• what is an advantage of the range?


  it's easier to calculate and understand than standard deviation
• what is a disadvantage of the range?


  it gives no information as to whether scores are clustered around the mean or evenly spread out unlike standard deviation

  it is also distorted by extreme values
• what is the mode?


  the most common score in a set of data
• if data has two modes, what do we call it?

  bimodal
• what do we say if a score has more than two modes?


  no modal score
• what is an advantage of the mode?


  not affected by extreme values, so can be used as an alternative for the mean which is affected by this
• 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 it's calculation
• what are the three measures of central tendency?


  mean, median and mode
• what is the median?


  the central number in a set of scores
• how can you calculate the median?


  by ranking the values in order of size then selecting the score that's in the middle, if there are more than two middle scores then add them together and divide them by 2
• what is an advantage of the median?


  it's not affected by extreme scores, so is a good alternative to the mean if this is the case
• what is a disadvantage of the median?


  it's not as sensitive as the mean because not all of the scores in a set of data are used in it's calculation
• what is the mean?


  the average of all of the scores
• how can you calculate the mean?


  by adding up all of the numbers in the set of data and divide this by the number of scores that there are
• what is an advantage of the mean?


  the most sensitive measurement as it uses all of the scores in a set of data
• what is a disadvantage of the mean?


  it can be affected by extreme scores, so if there is one smaller or larger score then this will distort the mean value