In 1999 the stock market took big swings up and down. A survey of 1,007 adult investors asked how often they tracked their portfolio. The table shows the investor respon the probability that an adult investor tracks his or her portfolio daily?
How frequently? Response
Daily
228
Weekly
278
Monthly
297
Couple times a year
147
Don't track
57
To find the probability that an adult investor tracks his or her portfolio daily, we need to divide the number of investors who track their portfolio daily (228) by the total number of adult investors surveyed (1,007).
Probability = Number of events of interest / Total number of events
Probability = 228 / 1,007
Probability = 0.2269
Therefore, the probability that an adult investor tracks his or her portfolio daily is approximately 0.227, or 22.7%.