Answer: 72.8%
Explanation:
Doubling my investment would mean increasing by 100% so that is the first return.
Halving my investment would mean reducing it by 50% so the second return is -50%.
Expected return is a weighted average based on the probabilities of the returns and is calculated as:
= (0.62 * 100%) + (0.38 * -50%)
= 0.43
Variance = (0.62 * (100% - 0.43)²) + (0.38 * (-50% - 0.43)²)
= 0.201438 + 0.328662
= 0.5301
Standard deviation = √0.5301
= 72.8%