Question

the table shows the movement of walt disney stock for 30 randomly selected trading days. “up” means the stock price increased in value for the day, and “down” means the stock price decreased in value for the day, and “no change” means the stock price closed at the same price it closed for the previous day. complete parts (a)-(e) below.
down down down down up up
down up down down up up
down down up up down up
down down down up up up
no change up down down no change no change
(c) what is the probability that walt disney stock is up for a randomly selected day?
0.400
(round to the nearest thousandth as needed.)
(d) is it unusual for walt disney stock to decrease in value for the day?
it blank unusual because for every 100 days, we can expect about blank of those days to show “down”.
(round to the nearest integer as needed.)

Explanation:

Step1: Count total number of days

There are 30 trading - days in total.

Step2: Count number of up - days

Count the number of "Up" in the data. Assume there are 12 "Up" days.

Step3: Calculate probability of up - days

The probability $P$ of an event is given by the formula $P=\frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}}$. So, $P(\text{Up})=\frac{12}{30}=0.400$.

Step4: Count number of down - days

Assume there are 15 "Down" days.

Step5: Calculate probability of down - days

$P(\text{Down})=\frac{15}{30}=0.500$.

Step6: Determine if down - days are unusual

An event is considered unusual if its probability is less than or equal to 0.05. Since $P(\text{Down}) = 0.500>0.05$, it is not unusual. For every 100 days, we can expect about $100\times0.500 = 50$ of those days to show "Down".

Answer:

(c) 0.400
(d) is not; 50