descriptive statistics

Question 1

measuring central tendency

Answer 1

Describe a data set by identifying one score that represents the general trend of data . There are three measures of central tendency

Question 2

Mode

Answer 2

Most common answer
strength:
it is useful when data are in categories, such as the number of babies who are securely attached
weaknesses:
it is not useful way of describing data when there are several modes

Question 3

Median

Answer 3

middle number when in order
strength:
it is not effected by extreme scores so can give a representative value
weaknesses
it is less sensitive that the mean as it dose not take into account all of the values

Question 4

mean

Answer 4

add all together and divide by how many there are
strength:
more sensitive than the median, it makes use of all the values of data
weaknesses
can be misrepresentative if there is an extreme value

Question 5

Measures of dispersion

Answer 5

these are measures that tell us whether scores in a set of data are similar to each other or if they are spread out. Range, variance, standard deviation

Question 6

Range

Answer 6

Difference between the highest and lowest numbers in a set of data
Remember some books define range the highest score minus the lowest score plus one
strengths
it is simply to calculate and takes account of extreme values
weaknesses
outliners can greatly influence the range
it ignores all but 2 of the scores, unlikely to provide an adequate measure of dispersion

Question 7

Variance

Answer 7

considers the difference between each data point and the mean this is called deviation.
These deviations are then squared, added together and the total is divided by the number of scores in the data set minus 1.

Question 8

Standard deviation

Answer 8

is a measure of dispersion which takes all the values in a set of data into account when it is calculated. It is like the mean in that we must assume that we have a normal distribution before it is reasonable to use it.
The formular is the square root of the variance

Question 9

level of measurement nominal

Answer 9

basic level of measurement , data is separated in categories such as grouping people according to height or data on their favourite colour

Question 10

level of measurement ordinal

Answer 10

data which can be ranked in order. There needs to be an increase in value of points along your data, but the size of each does not need to be equal.

Question 11

level of measurement interval

Answer 11

has no equal intervals, gives more than just order, they also show how much difference there is between the first and second and third and so on. Could be in cm, kilograms or seconds. A measurement of time not only tells he psychologist which participant is quickest