Phone Calls Survey
1. **Problem Statement:** Paula recorded the number of phone calls she received each day over a period of consecutive days. We need to find:
a) The total number of days the survey lasted.
b) The total number of calls received over this period.
c) The estimated probabilities of receiving:
i) No phone calls on a particular day.
ii) 5 or more phone calls on a particular day.
iii) Less than 3 phone calls on a particular day.
2. **Understanding the Graph:**
- The x-axis represents the number of calls per day (from 0 to 8).
- The y-axis represents the number of days Paula received that many calls.
- For example, the bar at 0 calls has height 2, meaning Paula received 0 calls on 2 days.
3. **Step a) Total number of days:**
Add all the days for each call count:
$$2 + 7 + 11 + 8 + 7 + 4 + 3 + 0 + 1 = 43$$
So, the survey lasted for **43 days**.
4. **Step b) Total number of calls:**
Multiply each number of calls by the number of days and sum:
$$0 \times 2 + 1 \times 7 + 2 \times 11 + 3 \times 8 + 4 \times 7 + 5 \times 4 + 6 \times 3 + 7 \times 0 + 8 \times 1$$
$$= 0 + 7 + 22 + 24 + 28 + 20 + 18 + 0 + 8 = 127$$
Paula received a total of **127 calls** over the 43 days.
5. **Step c) Estimating probabilities:**
Probability is estimated as \(\frac{\text{number of days with event}}{\text{total days}}\).
i) No phone calls (0 calls):
$$P(0) = \frac{2}{43} \approx 0.0465$$
ii) 5 or more calls (5, 6, 7, 8 calls):
Number of days = 4 + 3 + 0 + 1 = 8
$$P(\geq 5) = \frac{8}{43} \approx 0.1860$$
iii) Less than 3 calls (0, 1, 2 calls):
Number of days = 2 + 7 + 11 = 20
$$P(<3) = \frac{20}{43} \approx 0.4651$$
**Summary:**
- Survey lasted 43 days.
- Total calls received: 127.
- Probability of no calls on a day: about 4.65%.
- Probability of 5 or more calls: about 18.60%.
- Probability of less than 3 calls: about 46.51%.