Types of Distributions

• What is the most commonly referred to type of distribution?

  Normal distribution
• Why is the normal distribution often called the bell-shaped curve?

  Because it resembles the shape of a bell
• What does it mean for a normal distribution to be symmetrical?

  Left and right distributions match in frequency
• Which distributions commonly fall on a normal curve?

  Height, weight, IQ, blood pressure, shoe size
• Where do the mean, median, and mode fall in a normal distribution?

  They fall exactly in the center of the curve
• If the average height in the UK is measured, what would the graph resemble?

  A bell-shaped curve with most in the middle
• What are the definitions of mean, mode, and median in a normal distribution?

  • Mean: Average height in the population
  • Mode: Most common height in the population
  • Median: Middle value of height in the population
• What does it mean when data is described as "skewed"?

  It has a long tail on one side
• What is a negative distribution?

  Skewed to the left with a long tail
• How do the mean, median, and mode behave in skewed data?

  They will not be the same
• Where is the mean located in a skewed distribution?

  Closest to the tail of the distribution
• What are the characteristics of a positive skew distribution?

  • Long tail is on the right
  • Mean is closest to the tail
  • Mode is on the left
  • More low scores than high scores
  • Median lies between mode and mean
• What is the significance of standard deviation in a normal distribution?

  • Measures how spread-out scores are from the mean
  • Indicates percentage of scores within standard deviations:
  • 68% within 1 standard deviation
  • 95% within 2 standard deviations
  • 99.7% within 3 standard deviations
• What percentage of scores are within 1 standard deviation of the mean?

  68%
• What percentage of scores are within 2 standard deviations of the mean?

  95%
• What percentage of scores are within 3 standard deviations of the mean?

  99.7%
• What does the normal distribution of IQ scores indicate about the mean score?

  The mean score is 100
• If you score between 85 and 115 on an IQ test, where do you fall in the population distribution?

  You are within the 68% of the population
• If you score between 70 and 130 on an IQ test, what does this indicate?

  You are within 95% of the population
• What types of data can be normally distributed?

  • Height
  • Weight
  • IQ
  • Blood pressure
  • Shoe size