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CHAPTER 5

CHAPTER 5. Z-Scores. Z-Scores. The purpose of Z-scores or Standards Scores is to identify and describe the exact location of every score in a distribution. Ex. IQ score of 130 Characteristics of Z-Scores 1. The mean of the Z-scores is equal to zero .

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CHAPTER 5

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  1. CHAPTER 5 • Z-Scores

  2. Z-Scores • The purpose of Z-scores or Standards Scores is to identify and describe the exact locationof every score in a distribution. • Ex. IQ score of 130 • Characteristics of Z-Scores • 1. The meanof the Z-scores is equal to zero. • 2. Every distribution of Z-scores has standard deviation of 1. • 3. The Shapeof the distribution of Z-scores is identical to the shape of the distribution of raw scores.

  3. Z-Scores • Transformation of X values or individual scores into Z-scores serves 2 purposes • 1. It tells the exact location of the score within the distribution • 2. Scores can be comparedto other distributions that also have been transformed into Z-scores.

  4. Z-Scores • X= σ(Z)+µ • µ= X-σZ • σ= (X-µ)/Z • If X=60 • µ=50 • σ=5 Z=?

  5. CHAPTER 6 • Probability

  6. Probability • Number of times an event occurs in an infinite series of trials • P= #of times an event occurs/Total number of trials x100P=f/N x 100 • For probability to be accurate it is necessary to use random sampling.

  7. CHAPTER 6 • Probability

  8. Probability • Random Samplinghas 2 requirements: • 1. Each individual in the population must have an equal chance of being selected. • 2. If more than one individual or a group of individuals is to be selected for the sample there must be constant probability for each and every selection.

  9. Probability • Mega Ball/Power Ball= 1/259m • Lottery = 1/67m • Hit by Lightening = 1/10m • Victim of Crime in the U.S = 1/8000 Chance of dying in a flight 1/16m

  10. Violent Crime Comparison per 1,000 residents Your chances of becoming a victim in Florida 1 in 205 in Miami is 1 in 85

  11. Property Crime Rate Comparison per 1,000 residents Your chances of becoming a victim in Florida 1 in 31 in Miami 1 in 19

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