Question

Some statistics students estimated that the amount of change daytime statistics students carry is exponentially distributed with a mean of $0.72. Suppose that we randomly pick 25 daytime statistics students.

Find the probability that the average of the 25 students was between $0.79 and $0.97. (Round your answer to four decimal places.)
can you explained how can i solve this, using ti-84

Answer 1

for exponential distribution : mean =standard deviation =0.72

for normal distribution z score =(X-μ)/σ
here mean=       μ=	0.72
std deviation   =σ=	0.720
sample size       =n=	25
std error=σx̅=σ/√n=	0.14400

probability =P(0.79<X<0.97)=P((0.79-0.72)/0.144)<Z<(0.97-0.72)/0.144)=P(0.49<Z<1.74)=0.9587-0.6866=0.2722

(please try 0.2712 if this comes wrong)

if using ti-84 press 2nd -vars -use command :normalcdf(0.79,0.97,0.72,0.144)