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Scientific Inquiry SCI 105.020. Statistical Models and Probability. Recap: Ex 2.7. Analyze the findings reported in the May 8, 1987 issue of Science Identify the four components involved in Model Evaluation process

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Scientific inquiry sci 105 020

Scientific Inquiry SCI 105.020

Statistical Models and Probability

Recap ex 2 7
Recap: Ex 2.7

  • Analyze the findings reported in the May 8, 1987 issue of Science

  • Identify the four components involved in Model Evaluation process

  • Run the six-step program described in the text to summarize what you see from the report

The four components
The Four Components

Real World:

Dinosaurs extinct 65m-yr ago:

What caused it?



Single catastrophic


body hitting—caused it





Cracks in quartz +

Debris blocking sunlight for

months or years 

Climate cooled down 

Death of habitants on earth



Unique crack patterns

in quartz particles +

Unusually high concentration

of iridium found all over the world

Size and speed: fit or not?

The evaluation process
The Evaluation Process

  • RW: extinction of dinosaurs: What caused it?

  • Model: two alternative theories

    • Single catastrophic event  hit by an extraterrestrial body

    • A series of volcanic eruptions

  • (New) Data: found all over the world

    • Unique crack patterns in quartz particles, and

    • Unusually high concentration of iridium

  • Prediction:

    • same as what the new data shown

    • Size and speed prediction: seemed reasonable

  • Data-prediction agreement: GOOD  Model fit RW

Why statistical probabilistic models
Why Statistical/Probabilistic Models?

  • Widely used in science

    • Social/behavioral sciences

      • Public polls and surveys

      • Testing theories like: sunlight helps prevent depression

    • Bio-medical sciences

  • Can also be used in daily life

    • Professional sports:

      • AFC vs. NFC: which conference has stronger teams?

      • NBA: is the belief in “hot hand” supported by historical data?

Modeling with statistical hypothesis
Modeling with Statistical Hypothesis

  • Statistical hypothesis seem to be the only rational way to answer certain questions

    • What percentage of American women between the ages of 20 to 30 hold a full-time job?

      • Exceedingly difficult

      • Very costly

  • It’s impractical or even impossible to seek for characteristics in large populations

    • Instead, we can proximate them using small samples

Casual models casual hypothesis
Casual Models & Casual Hypothesis

  • Behavioral/bio-medical scientists concern about causes of characteristics exhibited by individuals

    • Does the dietary intake of cholesterol cause heart attacks in men?

  • Cause or Correlation?




The elements of a statistical study
The Elements of a Statistical Study

  • Terms associated with RW phenomenon

    • Population: the object of the investigation

    • A property is a characteristic that may exhibit in the population

      • Also known as a variable in the sense that it can be measured or classified to describe the property

      • Also known as a parameter as defined in the handout

  • Terms associated with model

    • Sample: selected members of the population

    • Statistics: a number computed from data that describes a characteristic of a sample

Stats as predictions to parameters
Stats as Predictions to Parameters

  • Theme:

    A statistic is computed from a sample to predict the parameter for the whole population.

  • Ex 1: average height of a Mercer Student


size: 8000+


Havg = XXX


havg = xxx


size: 200

Descriptive statistics
Descriptive Statistics

  • A graphical display of data

    • Histograms

  • Numerical summaries of data

    • Center

    • Spread

    • Shape

    • Outlier

      (See handout and sample

      worksheet for details)

Super Bowl Scores (1967-2001)


  • H/W Assignment 2

    • Ex 7: p 8 in the handout

      • Create a histogram

      • Draw a boxplot and more as specified

  • Read the sections 5.3 through 5.7 (pp 124-137) in Giere’s text