3.
Engle-Friedman and colleagues (2003)
studied the effects of sleep deprivation.
Fifty students were assigned to one night of sleep loss (students were required to call the
laboratory every half-hour all night) and then one night of no sleep loss (normal sleep). The
next day, students were offered a choice of math problems with differing levels of difficulty.
Following sleep loss, students tended to choose less challenging problems.
μn
<
μn

1.
10.36
Gender and number words:
Chang, Sandhofer, and Brown (2011)
wondered
whether mothers used number words more, on average, with their preschool sons than with their
preschool daughters. Each participating family included one mother and one child—either
female or male. They speculated that early exposure to more number words might predispose
children to like mathematics. They reported the following: “An independent-samples
t
test
revealed statistically significant differences in the percentages of overall numeric speech used
when interacting with boys compared with girls,
t
(30) = 2.40,
p
< .05,
d
= .88. That is, mothers
used number terms with boys an average of 9.49% of utterances (
SD
= 6.78%) compared with
4.64% of utterances with girls (
SD
= 4.43%)” (
pp. 444
–
445
).
1.
Is this a between-groups or within-groups design? Explain your answer.

2.
What is the independent variable? What is the dependent variable?

3.
How many children were in the total sample? Explain how you determined this.

4.
Is the sample likely randomly selected? Is it likely that the researchers used
random assignment?

5.
Were the researchers able to reject the null hypothesis? Explain.

6.
What can you say about the size of the effect?

7.
Describe how you could design an experiment to test whether exposure to more
number words in preschool leads children to like mathematics more when they enter school.

Collect information about number words used by mothers with their child while they
were in preschool, then perform a regression analysis and test the effect if number words
on the interest of children in mathematics when they enter grade school.