For a zero-coupon bond duration is approximately equal to the number of years to maturity. Here, there are 4 years until maturity, so the effective duration is approximately equal to 4 years. We use the term approximately because this ignores the curvature of the price/yield curve.

Duration is inversely related to yield to maturity (YTM). The higher the YTM, the lower the duration. This is because the change in the bond's price (or present value) is inversely related to changes in interest rates. When market yields rise, the value (or cash flow) of a bond decreases without decreasing the time to maturity.

Duration is also a function of volatility (risk).  Higher volatility (risk) = higher duration.  A higher coupon bond has a lower duration relative to a similar bond with a lower coupon because the bond holder is getting more of their cash value sooner (because of the higher coupon).  This lowers the overall risk of the bond resulting in a lower duration.

For coupon paying bonds, duration is less than maturity.

Duration is approximately equal to the point in years where the investor receives half of the present value of the bond's cash flows. Since zero-coupon bonds only have one cash flow at maturity, the duration is approximately equal to maturity. Any coupon amount will shorten duration because some cash flow is received prior to maturity.

The statement that a bond's percentage change in price and dollar change in price are both tied to the underlying price volatility is true.

The effective duration formula result is for a 1.00% change in interest rates (100 basis points equals 1.00%, or 0.01 in decimal form). The denominator is multiplied by 2.

The duration of a floating rate bond is equal to the time until the next coupon payment takes place. As the coupon rate changes semi-annually with the level of the interest rate, a floating rate bond has the same duration as a pure discount bond with time to maturity equal to the time to the next coupon payment of the floating rate bond.

The duration of a zero coupon bond is approximately equal to its time to maturity.

All else constant, a bond with a longer maturity will be more sensitive to changes in interest rates. All else constant, a bond with a lower coupon will have greater interest rate risk.

All else constant, a bond with a longer maturity will be more sensitive to changes in interest rates. All else constant, a bond with a lower coupon will have greater interest rate risk.