- selective subject loss/attrition

- expt=r effects

- demand characteristics

- placebo effects

- Hawthorne effects

- testing intact groups/lack of random assignment

- regression towards the mean

ceiling effect - truncation of data at the top of a distribution due to limit on highest possible score

floor effect - truncation of data at the bottom of a distribution due to limit on lowest possible score

ex. of a 2 x 2:

two levels of one IV - stats prep: didn't take Psy 302/did take Psy 302

two levels of other IV - sex: male/female

interaction--when the effect of one independent variable differs depending on the level of a second independent variable

Another example: sensitivity to various smells at different times of the day (morning and afternoon)
4 x 2 within subjects factorial design (each research participant smell 4 different vials, at two different times)  

	floral	sweaty	cinnamon	perfumey
A.M.
P.M.

1 continuous dep variable, 2 groups

(1 factor, 2 levels)

----> t-test

 

2 continuous variables, no groups

----> correlation (r)

 

1 continuous dep variable, 3 or more groups (1 factor/inde var, 3 or more levels)

----> ANOVA

(analysis of variance)

 

1 continuous dep variable, more than one set of 2 or more groups (more than one factor/inde var, each with 2 or more levels)

----> ANOVA

(analysis of variance)

 

categorical dep variable

-----> chi-square

F ratio =

                       explained variance (between groups)
                --------------------------------------------------
                          error variance (within groups)

Power= 1- beta

More power with
-- big N (number of subjects or data points)
-- big effect size
-- bigger alpha

- exact replication

- partial replication

Advantages of replication:
-- Helps reduce possibility of alpha error
-- Increases generalizability