Statistics Week 2

Statistics Week 2

1. Linking probability & distributions

   • Histogram tells us about data's probability distribution
   • Probability of picking someone within a particular range of the IV is based on the area under the appropriate distribution curve
   • The normal distribution - bell shaped, symmetric about the mean, area under curve always equal to 1
     • Never actually gets to 0 - gets very close by time it gets to 3 s.ds from the mean

2. Z Scores

   • A score from a normally distributed population can be transformed into a z-score
     • To do this, take the score (x) and subtract the population mean, then divide by the population s.d
       • Then use table to look up z-score & find p-value - proportion above score and below score
         • When z-score is minus -, look up positive (e.g -0.33, look up 0.33)
           • Also when its a minus, look at proportion above score, even if it's asking for probability of below
   • To convert back to x-score, multiply z-score by s.d and then add on mean