In an experimental study, men with erectile disorder received either Viagra or a placebo. In this study, the drug dosage (none versus peak
dose) was the
Select one:
O a confounding variable.
b. dependent variable.
c random sample.
d. independent variable.

Which of the following is an important function of child-directed speech? (a) it captures the infant’s attention and maintains communication. (b) it reduces the occurrence of infantile amnesia for the earliest memories of infancy. (c) it reduces the need for reciprocal interaction between caregivers and children. (d) it assists in prolonging rem sleep in infants.

[120 total points] (public health) in one of the largest human experiments ever conducted, in 1954 a randomized controlled trial was run to see whether a vaccine developed by a doctor named jonas salk was effective in preventing paralytic polio. a total of 401,974 children (ages 6–9), chosen to be representative of those who might be susceptible to the disease, were randomized to two groups: 200,745 children (the control group c) were injected with a harmless saline solution (a placebo) and the other 201,229 children (the treatment group t) were injected with salk’s vaccine.what was the point of giving saline solution to the children who didn’t get the vaccine? explain briefly.

4. decision trees are organized through a series of choose one answer. a. tiers b. the cut/dry method invented by the university of madagascar c. disorganized webs