Answer: True
Explanation:
Beta enables us to be able to calculate the risk of a stock in relation to how the market is moving. This is known as the systematic risk. Beta, needs to be calculated on based on the trading data of the stock.
If the stock is not publicly traded, it would not have the trading data required to find the beta. As we cannot get the beta, we would be unable it to calculate the return on stock and therefore the dividend growth model.