# AP Statistics Curriculum 2007 IntroVar

General Advance-Placement (AP) Statistics Curriculum - Introduction to Statistics

## The Nature of Data & Variation

No matter how controlled are the environment, the protocol or the design, virtually any repeated measurement, observation, experiment, trial, study or survey is bounded to generate data that varies because of intrinsic (internal to the system) or extrinsic (due to the ambient environment) effects.

For example, the UCLA's study of Alzheimer’s disease* analyzed the data of 31 Minor Cognitive Impairment (MCI) and 34 probable Alzheimer’s disease (AD) patients. The investigators made every attempt to control as many variables as possible. Yet, the demographic information they collected from the outcomes of the subjects contained unavoidable variation. The same study found variation in the MMSE cognitive scores even in the same subject. The table below shows the demographic characteristics for the subjects and patients included in this study, where the following notation is used M: male; F: female; W: white; AA: African American; A: Asian:

 Variable Alzheimer’s disease MCI Test statistics Test score P-value Age (years) 76.2 (8.3) range 52–89 73.7 (7.4) range 57–84 Student’s T to = 1.284 p=0.21 Gender (M:F) 15:19 15:16 Proportion zo = − 0.345 p=0.733 Education (years) 14.0 (2.1) range 12–19 16.23 (2.7) range 12–20 Wilcoxon rank sum wo = 773.0 p<0.001 Race (W:AA:A) 29:1:4 26:2:3 $\chi_{(df=2)}^2$ $\chi_{(df=2)}^2=1.18$ 0.55 MMSE 20.9 (6.3) range 4–29 28.2 (1.6) range 23–30 Wilcoxon rank-sum wo = 977.5 p<0.001

## Approach

Models and strategies for solving problems and understanding data and inferences.

• Once we accept that all natural phenomena are inherently variant and there are no completely deterministic processes, we need to look for models and techniques that allow us to study such acquired data in the presence of variation, uncertainty and chance.
• Statistics is the data science that investigates natural processes and allows us to quantify variation to make population inferences based on limited observations.

## Model Validation

Checking/affirming underlying assumptions.

• Each model or technique for data exploration, analysis and understanding relies on a set of assumptions, which always need to be validated before the model or analysis tool is employed to study real data (observations or measurements that are perceived or detected by the investigator).
• Such prior model conjectures or presumptions could take the form of mathematical constraints about the properties of the underlying process, restrictions on the study design or demands on the data acquisition protocol.
• Common assumptions include (statistical) independence of the measurements, specific limitations on the shape of the observed distribution, restrictions on the parameters of the processes being studied, etc.

## Datasets

There are a number of large, natural, useful and demonstrative datasets that are provided as part of this statistics EBook. Many of these data collections are intentionally selected to be large and complex. This choice is driven by the need of emphasizing the symbiosis between driving challenges, statistical concepts, mathematical derivations and the use of technology to solve relevant research problems.

## Examples

Computer simulations and real observed data.

## Hands-on activities

Step-by-step practice problems.