Tatyana is conducting an experiment where she gives participants a cup of regular or decaffeinated coffee and then asks them to complete a word-search puzzle. she wants to know if the amount of caffeine in the coffee will affect the time it takes to complete the puzzle. what is the independent variable in this study?

In the market for lock washers, a perfectly competitive market, the current equilibrium price is $5 per box. washer king, one of the many producers of washers, has a daily short-run total cost given by tc = 190 + 0.20q + 0.0025q2, where q measures boxes of washers. washer king's corresponding marginal cost is mc = 0.20 + 0.005q. how many boxes of washers should washer king produce per day to maximize profit?

Carlos wrote a check for $44.92 to pay his gas bill. he’ll use the check register to record his transaction. what will be his new balance?

The average u.s. household has $178,600 in life insurance. the standard deviation is $25,500. a local insurance agent would like to see how households in his city compare to the national average, and selects a simple random sample of 30 households from the city. for the households in the city, the average amount of life insurance is $188,800. a. based on the sample results, construct a 95% confidence interval for the true average amount of life insurance for households in the city. b. test the h0 : $178,600 ? ? to determine if the city's sample average is significantly different from the u.s. average amount of life insurance per household. use the conventional levels of significance.