Embed Size (px)
DESCRIPTION
Practice. 10.15 Did the type of signal effect response time?. t crit (15) = +/- 2.447 t obs = -2.24 Fail to reject Ho The type of signal does not have a significant effect on response time. New Step. Should add a new page Determine if One-sample t-test Two-sample t-test - PowerPoint PPT Presentation
Citation preview
Practice
• 10.15
• Did the type of signal effect response time?
• t crit (15) = +/- 2.447
• t obs = -2.24
• Fail to reject Ho– The type of signal does not have a significant
effect on response time.
New Step
• Should add a new page
• Determine if – One-sample t-test– Two-sample t-test
• If it is a dependent samples design
• If it is a independent samples with equal N
• If it is a independent samples with unequal N
Thus, there are 4 different kinds of designs
• Each design uses slightly different formulas
• You should probably make up ONE cook book page (with all 7 steps) for each type of design– Will help keep you from getting confused on a
test
• “My teacher is an idiot!”
• You wonder if the professors at Villanova are more intelligent than the average person. To examine this you collected data from 4 of your teachers. Determine if Villanova professors really have significantly ( = .05) higher IQs than the average IQ of the general population ( = 100).
Data
Person IQ
Dr. Brown 119
Dr. Kurtz 120
Dr. Blewitt 125
Dr. Toppino 180
Step 1: Write out Hypotheses
• Alternative hypothesis– H1: Prof > 100
• Null hypothesis– H0: Prof < or = 100
Step 2: Calculate the Critical t
• N = 4
• df = 3 = .05
• tcrit = 2.353
Step 3: Draw Critical Region
tcrit = 2.353
Step 4: Calculate t observed
tobs = (X - ) / Sx
Step 4: Calculate t observed
tobs = (X - ) / Sx
Sx = S / N
Step 4: Calculate t observed
tobs = (X - ) / Sx
14.73=29.45 / 4
Step 4: Calculate t observed
tobs = (X - ) / Sx
2.44 = (136 - 100) / 14.731.18=14.4 / 150
Step 5: See if tobs falls in the critical region
tcrit = 2.353
Step 5: See if tobs falls in the critical region
tcrit = 2.353
tobs = 2.44
Step 6: Decision
• If tobs falls in the critical region:
– Reject H0, and accept H1
• If tobs does not fall in the critical region:
– Fail to reject H0
Step 7: Put answer into words
• We reject H0 and accept H1.
• Professors at Villanova have significantly ( = .05) higher IQs than the average IQ of the general population ( = 100).
Practice
• 10.30– Are surgeons who have been sued more likely
to sound dominating than surgeons who have not been sued?
• Alpha = .05
• t crit (15) = -1.753
• t obs = -2.16
• Accept H1– Surgeons who sound dominating are more
likely to be sued (alpha = .05) than other surgeons.
Practice
• Sleep researchers decide to test the impact of REM sleep deprivation on a computerized assembly line task. Subjects are required to participate in two nights of testing. On each night of testing the subject is allowed a total of four hours of sleep. However, on one of the nights, the subject is awakened immediately upon achieving REM sleep. Subjects then took a cognitive test which assessed errors in judgment. Did sleep deprivation lower the subjects cognitive ability?
REM Deprived Control Condition26 2015 48 9
44 3626 2013 338 2524 1017 629 14
• tobs = 6.175
• tcrit = 1.83
• Sleep deprivation lowered their cognitive abilities.
