12 - Intro to Statistical Inference

# 12 - Intro to Statistical Inference - Chapter 12:...

This preview shows pages 1–8. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chapter 12: Introduction to Statistical Inference • Statistical Inference (drawing conclusion about population parameter from sample statistic) • Variety of research questions can ask about a single mean – Is mean of group different from a certain value? – Is mean higher (lower) than certain value? – Is mean between two values? • Start with hypothesis (e.g., population mean equals certain value) • What sample means would occur IF the hypothesis is TRUE • Obtain a random sample and compare mean with sampling distribution of the mean General Procedure for Hypothesis Testing • Step 1: Develop H and H A • Step 2: Find Mean of random sample • Step 3: Examine Sampling Distribution of Mean (values likely if H is true) • Step 4: Retain H if sample result is not sufficiently unlikely (by chance) to reject H Research Question • A developmental psychologist is interested in when young children acquire their first words. She knows that the national average age of first word utterances is 13 months, with a standard deviation of 2.75 months. She takes a random sample of 25 young children from her region to see how it compares to the average. Null and Alternative Hypothesis • Test the question in terms of Null and Alternative Hypotheses • Null ( H ) -- hypothesis researcher puts to the test – E.g., µ X = value • Alternative ( H A ) – contradictory hypothesis (usually hypothesis researcher wishes to support; e.g., µ X ≠ value) • Both H and H A are statements about population parameter • Decision is to reject or retain H • Reject H when observed mean is sufficiently unlikely to have occurred by chance if H is true Directional vs. Nondirectional Hypotheses • H A can be either directional or nondirectional • Nondirectional : Population parameter may be greater than or less than the value stated in H – Also known as a two-tailed test • Directional...
View Full Document

## This note was uploaded on 04/17/2008 for the course PSY 201 taught by Professor Arthur during the Spring '08 term at Purdue University.

### Page1 / 38

12 - Intro to Statistical Inference - Chapter 12:...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online