Distributions

Question 1

What is a normal distribution and give examples

Answer 1

• IQ, height , weight
• symmetrical bell shaped curve
• more ppt in the middle fewer on either side

Question 2

Measures of central tendency across a normal distribution

Answer 2

Mode: The highest point in a histogram is the most frequent score
Median:An equal number of scores on either side (symmetrical)
Mean: An equal number of outlier scores on either side.

Question 3

Characteristics of normal distribution - standard dev

Answer 3

68% of the scores in the data set fall within one standard deviation of the mean, 95% of the scores are within 2 standard deviations of the mean
Eg sm1 w an iq of 130 falls in top 2% of people and is 2 SD away from the mean

Question 4

Skewed distribution

Answer 4

Distribution of scores is asymmetric, most of the scores are on one side, with long skews/tails to the opposite of the maj scores

Question 5

Difference between positive and negative skew

Answer 5

Positive goes towards the right
Negative points towards the left

Question 6

Where are most of the scores and the outliers on the graph of positive and negative skew

Answer 6

Positive skew: More scores at the lower end of the graph, outliers at the higher end.
Negative skew: More scores at the higher end of the graph, outliers at the lower end.

Question 7

Measures of central tendency in skewed distributions

Answer 7

Mode: As the mode is the most frequent score, it remains at the highest point.
Median: At the point where 50% of the graph is either side (between mode & mean)
Mean: Shifted towards the outlier scores in the long tail (skew)