Last Minute AP Statistics

• How do you start every question

  Start every question by being precise and to the point. Leave room after each answer, so that you can add it later.
• What is the acronym for the distribution of a quantitative variable

  SCSU, soccer club surrey united.
• What does the first S in SCSU mean


  Shape
• What do you say for the first S in SCSU (example)

  We can see from the distribution that the shape is, roughly bell-shaped, symmetric and unimodal, right or left-skewed, bimodal.
• What does the first C in SCSU mean

  Center
• What do you say for the first C in SCSU (example)

  The median is 9 (or between 10-15 if it is a histogram) and mean (if you don't spend a lifetime to calculate mean) or you can mention and mean is lower or higher than median if it is right skewed or left skewed. Leave room for mode or for detailed calculation of mean etc.
• What does the second S in SCSU mean

  Spread
• What do you say for the second S in SCSU (example)

  The range is 25.7. Leave room for Q1 / Q3 etc.
• What does the first U in SCSU mean

  Unusual features
• What do you say for the first U in SCSU (example)


  Possible outliers (points A, C), clearly identified outliers (D,H) and there is a gap between E and F.
• What do you not mention in the confidence interval


  Don't mention null hypothesis for CI. They are not relevant.
• What is an alternative to mentioning the null in the confidence interval

  The interval does not contain 0, therefore, there is significant evidence that there is a significant difference between the means.
• What is a generic line for confidence interval


  We are 90% confident that the true mean lies within this confidence interval.
• What is the acronym for constructing and demonstrating confidence intervals

  PPCMC
• What does the first P in PPCMC mean (CI)

  Parameter
• What is an example of the first P in PPCMC (CI)


  The mean weight, proportion of all items, be specific, 500 gm butter packs, 300 ml milk bottles, percentage of soccer players in club A, proportion of heart patients in the city hospital). Use population parameters whenever possible, but can also use sample statistics.
• What does the second P in PPCMC mean (CI)

  Procedure, what type of interval is being introduced (ex. Two-sample t-interval).
• What is an example of the second P in PPCMC (CI)

  A two-sample t-interval, calculating for the difference in population means of BPA body concentrations in non-retail workers and retail workers
• What does the first C in PPCMC mean (CI)

  Check or conditions of inference.
• What is an example of the first C in PPCMC (CI)


  It is given that these are random samples. It is reasonable to assume that the samples are independent since both samples are large enough (>=30) so that the Central Limit Theorem applies making it approximately normal and it is reasonable to assume that the sample size are less than the 10% of the population
• What does the first M in PPCMC mean (CI)

  Mechanics
• What is an example of the first M in PPCMC (CI)


  Applying formula on calculator gives a confidence interval of (a,b) with df = 332.3. Explain what you have inputted into the calculator.
• What does the last C in PPCMC mean (CI)

  Conclusion
• What is an example of the last C in PPCMC (CI)


  We are 99% confident that the difference in true means of BPA body concentrations in all non-retail and retail workers is between a and b
• What happens if you see that only 50% of your sample items fall in your 95% confidence range

  That is perfectly fine as we are estimating sample mean, not individual items. We don't mean that 95% of individual items should fall within Confidence Interval. Also, there is no guarantee that the true population mean will be in this interval, but mostly it is true (so plausible is a better term)
• What do you use for null hypothesis

  The parameter is population proportion p or population mean µ. NEVER USE X bar or S.
• What is the acronym for hypothesis testing

  PPCMC
• What does the first P in PPCMC mean (HT)

  Parameter
• What is an example of the first P in PPCMC (HT)

  The parameter used is the difference in population means of satisfaction scores between two samples, i.e. µA for prof A and µB for prof B
• What does the second P in PPCMC mean (HT)

  Procedure
• What is an example of the second P in PPCMC (HT)

  A two-sample t-test for the difference in mean in satisfaction score for prof A and that of prof B.
• What does the first C in PPCMC mean (HT)

  Check
• What is an example of the first C in PPCMC (HT)

  The sample is random. The sample size is >=30, so the central limit theorem can be applied making the sampling distribution approximately normal. Reasonable to assume that the sample size is less than 10% of the population, making it independent.
• What does the first M in PPC
• MC mean (HT)

  Mechanics
• What is an example of the first M in PPCMC (HT)

  Ho: µA - µB =0, Ha: µA - µB >0
• What does the last C in PPCMC mean (HT)

  Conclusion
• What is an example of the last C in PPCMC (HT)

  Why you would accept or reject the null hypothesis. Probability of type 1 error, type 2 error [basically probability that the value falls where null hypothesis is accepted]. Language - There is sufficient evidence to reject Ho or we don't have sufficient evidence to reject Ho