সেশন ২/৩০

Population, Samples, Variables ও Data

একটা রো কী, একটা কলাম কী, আর প্রতিটি কলামের কাজ কী

১২০ মিনিট · ৬টি পর্বে ৪৩টি স্লাইড · স্লাইড ও নোট ইংরেজিতে

৩টি স্লাইড

Orientation

  1. Session 2 title slide: Population, Samples, Variables & Data.

    স্লাইড ১

    Population, Samples, Variables & Data

  2. Session 2, Orientation: Where we left it.

    স্লাইড ২

    Where we left it

  3. Session 2, Orientation: What you will be able to do at the end of today.

    স্লাইড ৩

    What you will be able to do at the end of today

৭টি স্লাইড

Act I · Your Question, Turned Into Rows and Columns

  1. Session 2, Act I · Your question, turned into rows and columns: Act I · Your question, turned into rows and columns.

    স্লাইড ৪

    Act I · Your Question, Turned Into Rows and Columns

  2. Session 2, Act I · Your question, turned into rows and columns: Your question.

    স্লাইড ৫

    Your question

  3. Slide introducing a study as a rectangle of rows and columns.

    স্লাইড ৬

    Every study becomes a rectangle

    Before any test, the data have a shape. Rows are the units you measured. Columns are the things you measured on them. The rest of the session lives inside that picture.

  4. Session 2, Act I · Your question, turned into rows and columns: Two questions to ask before any other.

    স্লাইড ৭

    Two questions to ask before any other

  5. Slide asking what one row of a dataset represents.

    স্লাইড ৮

    So what is one row?

    A row is not automatically a person. It is the unit the researcher decided to measure. Eyes, visits, households, and patients are different rows, and mixing them is how a paper quietly changes what it is about.

  6. Session 2, Act I · Your question, turned into rows and columns: The row you measured is not always the row you treated.

    স্লাইড ৯

    The row you measured is not always the row you treated

  7. Slide asking what one column of a dataset represents.

    স্লাইড ১০

    And what is one column?

    A column is one measured thing, with a type and a job. Until those two are named, a later table is just a pile of numbers with headings.

১২টি স্লাইড

Act II · Who the Study Is Actually About

  1. Session 2, Act II · Who the study is actually about: Act II · Who the study is actually about.

    স্লাইড ১১

    Act II · Who the Study Is Actually About

  2. Session 2, Act II · Who the study is actually about: Why not simply measure everybody?.

    স্লাইড ১২

    Why not simply measure everybody?

  3. Slide distinguishing four populations in a study.

    স্লাইড ১৩

    Four populations, not one

    Target, source, sampled, and analyzed are not synonyms. Papers collapse them into one word. The session pulls them apart so a later claim about ‘the population’ has to say which one.

  4. Session 2, Act II · Who the study is actually about: Who was let in, and who was kept out.

    স্লাইড ১৪

    Who was let in, and who was kept out

  5. Session 2, Act II · Who the study is actually about: How those 2,039 were picked.

    স্লাইড ১৫

    How those 2,039 were picked

  6. Session 2, Act II · Who the study is actually about: Who was never on the list at all.

    স্লাইড ১৬

    Who was never on the list at all

  7. Session 2, Act II · Who the study is actually about: The 229 people who never arrived.

    স্লাইড ১৭

    The 229 people who never arrived

  8. Slide distinguishing a parameter from a statistic.

    স্লাইড ১৮

    Parameter and statistic

    The parameter lives in the population you did not measure. The statistic lives in the sample you did. Session 1’s backwards arrow now has names on both ends.

  9. Slide showing the risky arrow from sample statistic to population parameter.

    স্লাইড ১৯

    Two worlds, and one risky arrow

    Everything later (standard error, confidence intervals, p values) is an attempt to say how much risk that arrow carries. Those tools are named and left. Today only names the two worlds.

  10. Session 2, Act II · Who the study is actually about: The notation, once, so it stops being decoration.

    স্লাইড ২০

    The notation, once, so it stops being decoration

  11. Session 2, Act II · Who the study is actually about: Three samples, three answers.

    স্লাইড ২১

    Three samples, three answers

  12. Session 2, Act II · Who the study is actually about: One substitution, so the symbols have somewhere to land.

    স্লাইড ২২

    One substitution, so the symbols have somewhere to land

১২টি স্লাইড

Act III · What Kind of Thing Is This Column, and What Job Does It Do?

  1. Session 2, Act III · What kind of thing is this column, and what job does it do?: Act III · What kind of thing is this column, and what job does it do?.

    স্লাইড ২৩

    Act III · What Kind of Thing Is This Column, and What Job Does It Do?

  2. Session 2, Act III · What kind of thing is this column, and what job does it do?: Back to the rectangle, because the rest of today lives in it.

    স্লাইড ২৪

    Back to the rectangle, because the rest of today lives in it

  3. Session 2, Act III · What kind of thing is this column, and what job does it do?: What kind of thing is this column?.

    স্লাইড ২৫

    What kind of thing is this column?

  4. Session 2, Act III · What kind of thing is this column, and what job does it do?: The boundary that is genuinely arguable: ordinal or discrete?.

    স্লাইড ২৬

    The boundary that is genuinely arguable: ordinal or discrete?

  5. Session 2, Act III · What kind of thing is this column, and what job does it do?: Sort these eight.

    স্লাইড ২৭

    Sort these eight

  6. Session 2, Act III · What kind of thing is this column, and what job does it do?: The answers, and the three that are worth arguing about.

    স্লাইড ২৮

    The answers, and the three that are worth arguing about

  7. Session 2, Act III · What kind of thing is this column, and what job does it do?: The same variable, twice, in two different types.

    স্লাইড ২৯

    The same variable, twice, in two different types

  8. Session 2, Act III · What kind of thing is this column, and what job does it do?: What a threshold costs you.

    স্লাইড ৩০

    What a threshold costs you

  9. Session 2, Act III · What kind of thing is this column, and what job does it do?: What the cut bought.

    স্লাইড ৩১

    What the cut bought

  10. Session 2, Act III · What kind of thing is this column, and what job does it do?: Where a column comes from.

    স্লাইড ৩২

    Where a column comes from

  11. Slide listing four jobs a column can do in a study.

    স্লাইড ৩৩

    Four jobs a column can do

    Outcome, exposure or predictor, confounder, and descriptor. The same blood-pressure column can do more than one job in two different papers. The job is a decision, not a property of the variable.

  12. Slide stating that exposure is a causal word and predictor is not.

    স্লাইড ৩৪

    Exposure is a causal word. Predictor is not.

    Calling a column an exposure is already a claim about the world. Calling it a predictor is not. The session makes that distinction early so later regression language cannot hide it.

৫টি স্লাইড

Act IV · The Role Is Not in the Column. It Is in the Question.

  1. Session 2, Act IV · The role is not in the column. It is in the question.: Act IV · The role is not in the column. It is in the question..

    স্লাইড ৩৫

    Act IV · The Role Is Not in the Column. It Is in the Question.

  2. Session 2, Act IV · The role is not in the column. It is in the question.: The same columns, two questions.

    স্লাইড ৩৬

    The same columns, two questions

  3. Session 2, Act IV · The role is not in the column. It is in the question.: Association, and what it is not.

    স্লাইড ৩৭

    Association, and what it is not

  4. Session 2, Act IV · The role is not in the column. It is in the question.: Four reasons two columns move together.

    স্লাইড ৩৮

    Four reasons two columns move together

  5. Slide showing an association in which smoking appears protective for hypertension.

    স্লাইড ৩৯

    In this study, smoking looks protective

    Among men in the Sylhet survey, current smokers had lower odds of hypertension. Nobody in the room believes smoking prevents high blood pressure. The point is the habit: an association is not a cause, and a paper that looks surprising is where the four reasons two columns move together become useful.

৪টি স্লাইড

Close

  1. Session 2, Close: Close.

    স্লাইড ৪০

    Close

  2. Session 2, Close: This is what you are going to write.

    স্লাইড ৪১

    This is what you are going to write

  3. Session 2, Close: The variable table has a professional name.

    স্লাইড ৪২

    The variable table has a professional name

  4. Session 2, Close: Before the next session.

    স্লাইড ৪৩

    Before the next session

নাম বলে রেখে দেওয়া

যা ইচ্ছে করেই এখনো পড়াইনি

  • Sample Size কত হওয়া দরকার (সেশন ১৭)।
  • Selection Bias ও Sampling Frame (সেশন ১৫ ও ১৬)।
  • Correlation ও Regression (সেশন ২৪)।

পরের সেশন

সেশন ৩: Categorical Data-র বর্ণনা

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Stat.BD