The article "‘little ice age’ proxy glacier mall balance records reconstructed from tree rings in the mt. waddington area, british columbia coast mountains, canada" (s larocque and d. smith, the holocene, 2005: 748–757) evaluates the use of tree ring widths to estimate changes in the masses of glaciers. for the sentinel glacier, the net mass balance (change in mass between the end of one summer and the end of the next summer) was measured for 23 years. during the same time period, the tree ring index for white bark pine trees was measured, and the sample correlation between net mass balance and tree ring index was r = −0.509. can you conclude that the population correlation rho differs from 0?