Answer:
Step-by-step explanation:
1) The z value was determined using a normal distribution table. From the normal distribution table, the corresponding z value for a 94% confidence interval is 1.88
The correct option is D
2) if 70% of all internet users experience e-mail fraud. It means that probability of success, p
p = 70/100 = 0.7
q = 1 - p = 1 - 0.7 = 0.3
n = number of selected users = 50
Mean, u = np = 50×0.7 = 35
Standard deviation, u = √npq = √50×0.7×0.3 = 3.24
x = number of internet users
The formula for normal distribution is expressed as
z = (x - u)/s
We want to determine the probability that no more than 25 were victims of e-mail fraud. It is expressed as
P(x lesser than or equal to 25)
The z value will be
z = (25- 35)/3.24 = - 10/3.24 = -3.09
Looking at the normal distribution table, the corresponding z score is 0.001
P(x lesser than or equal to 25) = 0.001
, so we know from the process of elimination that it will either be b or c. Next we have to realize that if the parabola opens to the left it is a negative parabola, just like if a parabola opens upside down it is a negative parabola. So the one that has the negative out front is b.