A group of college students is participating in a memory study that involves performing the same task each day under different circumstances; however, as each day goes by, the students are obviously getting more comfortable with completing the task. Which threat to internal validity has confounded this study?

In 1990, the average income for an american worker was $1,518 per month. in 2000, the average income for an american worker was $2,632 per month. during this time period, a basket of necessities (food, housing, etc.) increased from $657 per month in 1990 to $1,402 per month in 2000. the real value of income ▼ increased decreased over that 10-year period.

The chart shows the marginal cost and marginal revenue of producing apple pies. what most likely will happen if the pie maker continues to make additional pies? the marginal costs will continue to rise, increasing the total cost, while the marginal revenue remains the same, decreasing the profit. the marginal costs will continue to fall, decreasing the total cost, while the marginal revenue remains the same, increasing the profit. the marginal costs will continue to rise, increasing the total cost, while the marginal revenue remains the same, increasing the profit. the marginal costs will continue to fall, decreasing the total cost, while the marginal revenue remains the same, decreasing the profit.

Why is the netherlands vulnerable to changes in climate? a. the netherlands is against nuclear power. b. forests in the netherlands have been destroyed by acid rain. c. the netherlands wrote the kyoto protocols. d. the netherlands is low-lying country, and rising sea levels may cause flooding.