In an experiment to determine the effect of curing time on compressive strength of concrete blocks, two samples of 15 blocks each were prepared identically except for curing time. The blocks in one sample were cured for two days, while the blocks in the other were cured for six days. The compressive strengths of the blocks, in MPa, are as follows:

Can you conclude that the mean strength is greater for blocks cured for six days?

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Cured 2 days (X): 1326 1302 1314 1270 1287 1328 1318 1296 1306 1329 1255 1310 1255 1291 1280 Cured 6 days (Y): 1387 1301 1376 1397 1399 1378 1343 1349 1321 1364 1332 1396 1372 1341 1374