Stat 217 – Day 22Last Time – Subtle IssuesLast TimeFormat of ExamTypes of Calculation ProblemsTest of Significance Steps (bottom p. 338)Confidence Interval StepsShowing workTypes of Interpretation ProblemsHW CommentsCommon MistakesAdviceStudent Recommended StrategiesStat 217 – Day 22ReviewLast Time – Subtle IssuesMake sure you have a random sample or interval doesn’t tell you much!Make sure you have a sample!Don’t need a CI when know parameterStatistical vs. practical significanceStrong evidence vs. big differenceDuality of test and confidence intervalMean vs. mostFail to reject H0 vs. it’s true!Last TimeIf all else is the same:Smaller s will have smaller p-value and shorter confidence intervalLarger n will have smaller p-value and shorter confidence intervalUsing appletLet me know which procedureCan ignore Ho, Ha, test statistic, p-value if only need CI. Inputs requiredFormat of ExamCan bring two (two-sided) pages of notes that either I gave you or you self-producedPrepare as if closed bookWork efficientlyStill bring calculatorBe able to read computer outputBe able to carry out calculations using appropriate appletsTypes of Calculation Problems1. Probability calculations for normal distributionGiven mean and standard deviation2. Probability calculations for a sampling distribution (CLT)E.g., if = .2, what is the probability < .1Sketch (and label) distribution3. Test of significance (6 steps)Is there statistically significant evidence that…4. Confidence interval (4-5 steps)Estimate the population parameter…pˆTest of Significance Steps (bottom p. 338)1. Define parameter in words2. State Ho and Ha hypotheses about parameter3. Check technical conditions Be able to sketch sampling distribution if met4. Calculate test statistic5. Use technology to determine p-value6. Make conclusion: evaluate p-value, reject or fail to reject Ho, and answer the research question in contextConfidence Interval Steps1. Define parameter in words2. Check technical conditions 3. Use technology to determine the interval4. Interpret the interval… I’m 90% confident that…5. If asked, interpret “confidence” without using “confidence”Showing workBy hand: show formula, numbers plugged inApplets: which one, which option (e.g,. “one mean”), numbers plugged inNormal probability CalculatorTest of Significance Calculatorp-value and confidence intervalNOT “Simulating confidence intervals”Types of Interpretation ProblemsPopulation vs. sample vs. sampling distributionInterpret probability, confidence interval, confidence level, p-value…Including “what if”Identify appropriate proceduresScope of conclusions (generalizability, causation)Why?HW CommentsParameter vs. populationDefining parameter (“all” or “population”…)EV vs. RVConclusion in English/contextThe population mean …This didn’t happen by chance alone…Two populations/samplesVs. groups, Vs. “the sample size is large enough”CI: Which population has higher mean/proportionDirection of subtraction, All negative values implies…Technical conditionsStating vs. checkingRandom sample check!Common MistakesQuantitative vs. categoricalSymbols: vs. (be able to define in words)Technical conditions z-procedures with proportions, t-procedures with meansDon’t combine: “mean proportion”Stating hypotheses about statistic/nothingH0: = .5Sample size checksvs. population check. What’s “normal”?What changes when you increase the sample size…Parameter vs. statistic, sample vs. sampling distnStopping at “reject Ho” decision…AdviceW o rk problems, don’t just read them!Using only notes pages, calculatorStart with a pictureSee if you can identify problem typeThink about what each step meansBanish the words IT, proof, dataAdd the phrase “of what” and “for what”Learn from/seek clarification of grader commentsHW, labs, TIA activities, etc.Topic summaries, Self-check, Watch Out pointsStudent Recommended StrategiesStudy group (visual referent)Old material, homeworks, and practice problemsStudy in advance, relax day ofStudy guide, boxed items, watch out sectionsDoing other (new) problems in text, reading labsVocabulary Feedback on how to format responses, see where lost pointsMaking the note
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