Descriptive Stats, Variance and Standard Deviation

What is the mean?

• Average of numbers

• Used by adding up all scores and dividing by the number of scores

What is the median?

• The middle number

• Calculated by finding the middle score when putting all scores in numerical order

• If there is an odd number of results, the media is the middle number

• If it is even, the median is the mean of the middle two numbers

What is the mode

• The most frequently appearing value

• When there is more than one value that appears the most, it is called bimodal

What are the measures of central tendency?

• Mean

• Median

• Mode

When is it suitable and not suitable to use the mean?

• Suitable: Uses all the data so is the most sensitive value

• Not suitable: When there are extreme values and outliers as the mean is skewed

When is it suitable and not suitable to use the median?

• Suitable: When there are extreme values, the median is less affected

• Not suitable: Less sensitive to variations in data so may not be a true representation

When is it suitable and not suitable to use the mode?

• Suitable: When there is categorical/nominal data as the others are not appropriate

• Not suitable: There may be no modal value or several

What are the measures of dispersion?

• Range

• Variance

• Standard deviation

What is the range?

• The difference between the highest and lowest scores

• Calculated by subtracting the lowest score from the highest score

What is variance and what does it show?

• Spread of scores around the mean

• Small variance means the scores are similar and close to the mean

• Large variance shows scores are a larger distance apart

What is standard devaition?

• SD is the square root of the variance

• It tells use the average amount a number differs from the mean

What is the equation for variance and standard deviation?

• x is the individual score

• The x with the line over is the mean score

• n is the number of participants