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PSYC227_fall09_week8

# PSYC227_fall09_week8 - Hypothesis Testing...

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Was it due to chance, or something else? Hypothesis Testing

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Hypothesis Tes8ng Step 1: state the hypothesis Step 2: set the criteria for a decision Step 3: Collect data and compute sample sta8s8cs Step 4: make a decision A hypothesis test is a statistical method that uses sample data to evaluate a hypothesis about a population. Was it due to chance, or something else? Standardized method for evalua8ng the results of a research study.
Step 1: state the hypothesis The Null hypothesis (H 0 ) : observed difference reﬂects chance varia8on ( zero effect ) The Alterna1ve hypothesis (H 1 ) : observed difference is real ≠, two‐tailed <, > one‐tailed (direc8onal) H 0 and H 1 are mutually exclusive! No change

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Select an alterna1ve hypothesis as that which the sampling experiment is intended to establish . There are 3 possibili8es One‐tailed, upper‐tailed > One‐tailed, lower‐tailed < Two‐tailed Select the null hypothesis as the status quo. One‐tailed: parameter value closest to the alterna8ve Two‐tailed: complementary (only unspecified) value Step 1: state the hypothesis No change
Example: set up the null and alterna8ve hypothesis for tes8ng the claim: Science (1999) reported that the mean listening 8me of 7‐ month‐old infants exposed to a three‐syllable sentence is 9 seconds.

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H 0 : µ = 9 H 1 : µ ≠ 9 Example: set up the null and alterna8ve hypothesis for tes8ng the claim: Science (1999) reported that the mean listening 8me of 7‐ month‐old infants exposed to a three‐syllable sentence is 9 seconds.
Infants exposed to cocaine in their mother’s womb are thought to be at a high risk for major birth defects. However, according to a University of Florida study, more than 75% of all cocaine‐exposed babies suffer no major problems. Example: set up the null and alterna8ve hypothesis for tes8ng the claim:

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Infants exposed to cocaine in their mother’s womb are thought to be at a high risk for major birth defects. However, according to a University of Florida study, more than 75% of all cocaine‐exposed babies suffer no major problems. H 0 : µ = 0.75 H 1 : µ > 0.75 Example: set up the null and alterna8ve hypothesis for tes8ng the claim:
According to the Journal of Psychology and Aging , older workers (45 years old or older) have a mean job sa8sfac8on ra8ng of 4.3 on a 5 point scale. Example: set up the null and alterna8ve hypothesis for tes8ng the claim:

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According to the Journal of Psychology and Aging , older workers (45 years old or older) have a mean job sa8sfac8on ra8ng of 4.3 on a 5 point scale. H 0 : µ = 4.3 H 1 : µ 4.3 Example: set up the null and alterna8ve hypothesis for tes8ng the claim:
Example: diet effect A researcher is using a sample of 16 rats to examine the effect of a new diet drug. Under regular circumstances, rats eat an average of 10gm of food each day. The distribu8on of food consump8on is normal with SD=4. The expected effect of a drug is to reduce food consump8on . The purpose of the experiment is to determine if the drug works .

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PSYC227_fall09_week8 - Hypothesis Testing...

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