1. **Stating the problem:**
We have a survey where 75% of Information Technology students have eWallets. From a random sample of 150 students, we want to find:
i. The probability that at most 70% have eWallets.
ii. The probability that at least 35% did not have eWallets.
2. **Understanding the problem:**
Let $p=0.75$ be the true proportion of students with eWallets.
Sample size $n=150$.
3. **Using the normal approximation to the binomial distribution:**
Since $n$ is large, the sampling distribution of the sample proportion $\hat{p}$ is approximately normal with mean $\mu = p = 0.75$ and standard deviation $\sigma = \sqrt{\frac{p(1-p)}{n}} = \sqrt{\frac{0.75 \times 0.25}{150}}$.
Calculate $\sigma$:
$$\sigma = \sqrt{\frac{0.75 \times 0.25}{150}} = \sqrt{\frac{0.1875}{150}} = \sqrt{0.00125} \approx 0.03536$$
4. **Part i: Probability at most 70% have eWallets**
We want $P(\hat{p} \leq 0.70)$.
Calculate the z-score:
$$z = \frac{0.70 - 0.75}{0.03536} = \frac{-0.05}{0.03536} \approx -1.414$$
Using standard normal tables or calculator, $P(Z \leq -1.414) \approx 0.0785$.
5. **Part ii: Probability at least 35% did not have eWallets**
Since 35% did not have eWallets, the proportion with eWallets is at most 65%.
So, $P(\hat{p} \leq 0.65)$.
Calculate the z-score:
$$z = \frac{0.65 - 0.75}{0.03536} = \frac{-0.10}{0.03536} \approx -2.828$$
Using standard normal tables or calculator, $P(Z \leq -2.828) \approx 0.0023$.
**Final answers:**
- Probability at most 70% have eWallets is approximately 0.0785.
- Probability at least 35% did not have eWallets is approximately 0.0023.
Ewallet Probability 748F18
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