Parametric Techniques - Introduction

Introduction to Parametric Techniques

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Online Course Pharmaceutical Biostatistics Chapter 4: Parametric Techniques

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Statistical Analysis

Parametric “parametric”=parameter or characteristic of a population.

-t-tests -Analysis of variance • Normally distributed •More robust than nonparametric test

Non-parametric Less “fussy”.

Less sensitive -Ideal for use when you have data that are measured on nominal (categorical) and ordinal (ranked) scales.

-small samples -data do not meet the stringent assumptions of parametric techniques.

-Also known as distribution free tests 17/7/2017

Online Course Pharmaceutical Biostatistics Chapter 4: Parametric Techniques

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Parametric vs Non-Parametric Tests

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Two types of statistical techniques used to generalize data from samples to population.

1.

Parametric: Data must be at least interval (continuous / scales) and the distribution must be NORMAL.

2.

Non-parametric: The data is at least interval but the distribution is not NORMAL or the data is categorical (nominal / ordinal).

Online Course Pharmaceutical Biostatistics Chapter 4: Parametric Techniques

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Parametric vs Non-Parametric Tests Parametric test

Non-parametric test

-Data: Ratio (eg: distance,in kilometer) and Interval (eg: oC)

- Data: Nominal(eg: race, gender) and ordinal (eg: satisfaction)

- Normally distributed

- Not Normally distributed

- Based on mean and standard deviation

-Based on frequency and median

Test: • t-tests •ANOVA •Pearson correlation

Test: • Chi-Square-For nominal • Mann-Whitney U, Kruskal-Wallis H, Wilcoxon T, Friedman and Correlation Spearman

17/7/2017 Online Course Pharmaceutical Biostatistics Chapter 4: Parametric Techniques

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Classification of Univariate Technique

Interval/Ratio Data

One sample

Independent

-Z/t test -One-way ANOVA

2 or more samples

Related

-Paired samples t-tests - Repeated measure

Nominal/ Ordinal Data

One sample

2 or more samples

Independent

Related

-Chi Square -Mann Whitney -Median -K-S -K.W ANOVA 17/7/2017

Online Course Pharmaceutical Biostatistics Chapter 4: Parametric Techniques

-Sign -Wilcoxon -McNemar 5

MEASUREMENT SCALE Measurement scale

Examples

RATIO Has a meaningful zero point (physical)

-Height -Weight -Time -Speed

INTERVAL Predetermined equal intervals, no true zero point

-Score: Achievement, IQ, Temperature

ORDINAL Classifies and ranks objects

Opinion: Academic level, income level, degree of liking

NOMINAL Classifies objects into categories

True Categories: Taste, gender, ethnicity, color Artificial Categories : Color type (soft, bold) Weather (hot, cool) 17/7/2017

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Online Course Pharmaceutical Biostatistics Chapter 4: Parametric Techniques

Characteristics of Normal Distribution

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Two types of statistical techniques used to generalize data from samples to population.

1.

Parametric: Data must be at least interval (continuous/ scales) and the distribution must be NORMAL.

2.

Non-parametric: The data is at least interval but the distribution is not NORMAL or the data is categorical (nominal/ordinal).

Online Course Pharmaceutical Biostatistics Chapter 4: Parametric Techniques

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Skewness and kurtosis must be zero for normal distribution

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Online Course Pharmaceutical Biostatistics Chapter 4: Parametric Techniques

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