Stats - Statistics 350 Notes Final Exam Study Guide Chapter...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Statistics 350 Notes Final Exam Study Guide Chapter 2 : Variable – a characteristic that differs from one individual to the next Categorical variable – places an individual into one of several groups or categories; if it has ordered categories, it is called an ordinal variable (seat location, current smoker, soft drink size, etc.) Quantitative variable – numerical values (age, number of CDs owned, times spent talking on cell phone, etc.) Explanatory vs. response variables – which causes the other? Shapes: bell-shaped, uniform, skewed, unimodal, bimodal Skewed right = tail is on right, median is less than mean Skewed left = tail is on left, mean is less than median Location (center, average): approximate middle value Spread (variability): standard deviation, range Outliers – points that are not consistent with the bulk of the data Mean – the numerical average value (mean of a sample = x-bar) The mean is sensitive to extreme observations The median is resistant to extreme observations Median = 50 th percentile, Q 2 First quartile = 25 th percentile, Q 1 Third quartile = 75 th percentile, Q 3 Interquartile range (IQR *middle 50% of data) = Q 3 - Q 1 Check for outliers by using the 1.5*IQR rule (Q 3 /Q 1 – 1.5*IQR) Boxplots: cannot confirm shape Normal Distributions Standard deviation – the measure of the spread of the observations from the mean (roughly, the average distance the observations fall from the mean) Variance = s 2 , standard deviation = s Interpretation of the standard deviation: The weights of small orders of French fries are roughly 6 grams away from their mean weight of 73.6 grams, on average. Standard deviation is sensitive to outliers and extreme observations
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Empirical Rule – For bell-shaped curves, approximately… 68% of the values fall within 1 standard deviation from the mean in either direction 95% of the values fall within 2 standard deviations from the mean in either direction 99.7% of the values fall within 3 standard deviations from the mean in either direction Standardized scores (z-score) – the distance between the observed value and the mean, measured in terms of the number of standard deviations Z-score = (observed value – mean) / standard deviation Chapter 3 : Selection bias – if the method for selecting the participants produces a sample that does not represent the population of interest Nonresponse bias – when a representative sample is chosen for a survey, but a subset cannot be contacted or does not respond Response bias – when participants respond differently from how they truly feel (wording of the question, the way an interviewer behaves, etc. might lead an individual to provide false information) Margin of error – the measure of accuracy in sample surveys (how close that proportion comes to t he truth for the entire population) Chapter 4 Observational studies – researches simply observe or question the participants about opinions, behaviors, or outcomes
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern