¥ can then be subtracted from X to determine whether there is any significant difference between the two quantities: X~Y¥ = (3.28-3.252/ (0.28)* + (0.29)"] x 107 = 0.03 + 0.40) x 1074 Since this difference is considerably less than the standard error, it can be assumedthat, within the accuracy of the measurements and the measuring instruments, there was no significant difference in the peak pressure measured at equidistant points along two different azi- muths from ground zero. Therefore it can be concluded that along these two radii the shock wave exhibited marked symmetry. ~ REFERENCES 1. P. E. Shafer, A Copper Indenter Gauge for Air Blast Measurement, Sandstone Report, Annex 5, Vol. 21, Part U, June 1948. 2. P. E. Shafer and E. R. Walthall, A Copper Indenter Gauge for the Measurementof Air Blast Peak Pressures, Naval Ordnance Laboratory Report, NavOrd-2192, July 1951. 3. R. R. Caforek, Evaluation of Copper-Dise Indenter Gauge in Measurement of Peak Pressure and Pressure Ratio of Small Charges, Naval Ordnance Laboratory Report, NavOrd-2170, September 1951. i | | 67