What is the best way to avoid data-snooping bias?

Which of the following statements is (are) true with respect to the price behavior of putable bonds?
I). At very high levels of interest rates, the price of a putable bond will be very close to that of an equivalent non-putable bond.
II). At very low levels of interest rates, the put embedded in the bond will have a very low value.
III). Negative convexity will begin to appear for a putable bond at very low yield levels.
IV). At high yield levels, duration will underestimate the expected bond price for a given unit change in yield.

Margin loans may increase the purchase of stocks. Declining margin debt may force the selling of stocks. This is using margin debt as a:

Which of the following would be an effect of capitalizing interest costs?
I). Depreciation is understated.
II). Interest coverage would be understated.
III). Cash flows from investing are understated.
IV). Cash flows from operations are understated.

Which of the following characteristics is not representative of an industry that's in the maturity stage of its life cycle?