A sample of 20 students who had recently taken elementary statistics yielded the following information on brand of calculator owned. (T = Texas Instruments, H = Hewlett Packard, C = Casio, S = Sharp):H T T S S S H T T TS H S S C H C H C T(a) Estimate the true proportion of all such students who own a Texas Instruments calculator.(b) Of the 6 students who owned a TI calculator, 5 had graphing calculators. Estimate the proportion of students who do not own a TI graphing calculator.

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.