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In cricket, a batsman will be not out if he comes out to bat in an innings and has not been dismissed by the end of the innings. One may similarly describe a batsman as not out while the innings is still in progress. A batsman's score is often appended with an asterisk to indicate that he was not out; for example, '10*' is read '10 not out'.
At least one batsman will be not out at the end of an innings, because once ten batsmen are out, the eleventh will have no partner to bat on with. Two batsmen will be not out if a declaration is made in first-class cricket, and often at the end of the scheduled number of overs in limited overs cricket. A batsman further down the batting order than the not-out batsmen will not come out to the crease at all and is noted as did not bat rather than not out; by contrast, a batsman who comes to the crease but faces no balls is not out. A batsman who retires hurt is considered not out; an uninjured batsman who retires is considered retired out.
Batting averages are calculated as runs divided by outs, which means that a player who often ends the innings not out may get an inflated batting average. Examples of this include Michael Bevan (67 not outs in ODIs), James Anderson (12 not outs in 16 Test innings), and Bill Johnston topping the batting averages on the 1953 Australian tour of England. However, the flip side of the argument is that, if not outs were counted for the purpose of batting averages, a good batsman could come in and only have time to make 0 not out, facing three balls from a bowler, and thus get unduly penalised for factors out of his control. This argument is prevailing among cricket statisticians, who have used this method of collecting batting averages since the 18th century. Furthermore, a batsman will tend to be at his most vulnerable early in an innings before he has "got his eye in"; as a result it may be considered a greater achievement to achieve two scores of 20 not out and 20 (averaging 60) than to make one score of 40, since in the latter instance the batsman will only have had to negotiate the start of one innings.