Lesson 6 of 6 · All lessons in this module
- Why options need a price model: the one-period binomial setup
- The hedge ratio and the riskless portfolioVideo lesson
- From the riskless hedge to the option price
- Risk neutrality and risk-neutral probabilitiesVideo lesson
- What does and does not move a binomial option value
- Integrated cases: an underpriced put and a tree with a negative rate
Lesson 6 of 6 · 14 min
Integrated cases: an underpriced put and a tree with a negative rate
A binomial case hands you a data panel and chains the questions: read the tree, find the hedge ratio and π, price the option, then test the quote against the model or price it with a risk-free rate that may be negative.
In short
- Read the panel in order: the two end prices, the option's payoff in each state, the rate for the period (not the annual rate), then the quoted price.
- Get h* from the payoffs alone. For a put it is negative, so the put and the shares are bought (or sold) together.
- Value with and discount at ; cross-check by replication or put-call parity.
- An underpriced option is bought with its hedge. The hedge's riskless return is end value ÷ total outlay − 1, and it is compared with r, not with zero.
- A negative rate does not change a formula: is simply below 1, so π is lower and discounting adds value.
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