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):
| T |
C |
S |
S |
T |
T |
H |
S |
T |
T |
| C |
T |
T |
H |
H |
T |
C |
C |
T |
S |
(a) Estimate the true proportion of all such students who own a Texas Instruments calculator.
(b) Of the 9 students who owned a TI calculator, 4 had graphing calculators. Estimate the proportion of students who do not own a TI graphing calculator.