One popular activity that tourists participate in when they visit Alaska is panning for gold. A gift shop by the panning center sells blocks of clay. The packaging on the clay claims that one in five blocks contains gold. A frequent purchaser of this item believes that this is an overstatement. To investigate, he purchases a random sample of 50 blocks from the large display in the store and finds that 8 of the blocks contain gold.

Based on this sample, is there convincing evidence that the true proportion of blocks that contain gold is less than 0.20? Use ???? = 0.10. Provide statistical evidence to support your answer.