# PSY201H1 Lecture Notes - Lecture 9: Standard Score, Percentile Rank, Statistical Inference

## Document Summary

The probability given in the unit normal table will be accurate only for normal distribution scores so the shape of the distribution should be verified before using it. Look up the proportions corresponding to the z score value. Percentile rank is the percentage of individuals in the distribution who have scores that are less than or equal to a specific score. Probability questions can be rephrased as proportion and percentile questions. Cannot go directly from x value to proportion. Knowing the probability that a z score will occur can help you determine how extreme a z score you can expect before determining that a factor other than chance produced the outcome. P help determine how unlikely this event might be. Less 5% chance occuring = rare/extreme = significant. Many research questions begin with a population that forms a normal distribution. A random sample selected and receives a treatment to evaluate the treatment.