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A Performance Analysis System for the Sport of Bowling

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3.5 ASSUMPTIONS AND ERROR ANALYSIS<br />

The derivations behind <strong>the</strong> MASTER calculations presented in <strong>the</strong> previous discussion<br />

rely heavily on several basic assumptions, some <strong>of</strong> which have already appeared in o<strong>the</strong>r<br />

sections throughout <strong>the</strong> course <strong>of</strong> <strong>the</strong> paper. This section presents <strong>the</strong> analysis<br />

assumptions in detail, along with an assessment <strong>of</strong> <strong>the</strong>ir possible error contributions.<br />

3.5.1 Distance<br />

Throughout <strong>the</strong> paper, it has been assumed that <strong>the</strong> ball travels 60 feet - <strong>the</strong> distance from<br />

<strong>the</strong> foul line to <strong>the</strong> head pin. Under normal circumstances, release <strong>of</strong> <strong>the</strong> ball occurs close<br />

to <strong>the</strong> foul line, and <strong>the</strong> first pin <strong>the</strong> ball encounters is <strong>the</strong> head pin (at least on <strong>the</strong> first<br />

ball <strong>of</strong> any frame). It is time to take a closer look at what this assumption entails.<br />

• The ball is released at <strong>the</strong> foul line: An error factor is introduced in <strong>the</strong> average<br />

linear velocity calculation if <strong>the</strong> ball is released behind <strong>the</strong> foul line (<strong>the</strong> actual<br />

velocity will be higher than calculated), or beyond <strong>the</strong> foul line (<strong>the</strong> actual<br />

velocity will be lower than calculated). Generally, <strong>the</strong> bowler releases <strong>the</strong> ball at,<br />

or just beyond, <strong>the</strong> foul line. For a legal delivery, no part <strong>of</strong> <strong>the</strong> bowler's body<br />

may touch <strong>the</strong> lane beyond <strong>the</strong> foul line. This presents a physical limitation on<br />

release beyond <strong>the</strong> foul line <strong>of</strong> approximately 12 inches.<br />

Additional error is possible from behind <strong>the</strong> foul line, usually resulting from a<br />

noticeable lapse in execution on <strong>the</strong> bowler's part (dropping <strong>the</strong> ball, releasing <strong>the</strong><br />

ball early, or stopping short <strong>of</strong> <strong>the</strong> foul line). Although <strong>the</strong> module can not detect<br />

<strong>the</strong> absolute point <strong>of</strong> release, it does indicate when <strong>the</strong> ball hit <strong>the</strong> lane, in relation<br />

to release. In addition, <strong>the</strong> bowler easily recognizes when <strong>the</strong>se major lapses in<br />

execution occur, and can take note <strong>of</strong> <strong>the</strong>m.<br />

The nominal margin <strong>of</strong> error at <strong>the</strong> point <strong>of</strong> release is estimated to be ±6", with <strong>the</strong><br />

vast majority <strong>of</strong> releases occurring within a ±3" range.<br />

• The ball hits <strong>the</strong> head pin at a fixed location: At <strong>the</strong> o<strong>the</strong>r end <strong>of</strong> <strong>the</strong> lane, <strong>the</strong><br />

ball can hit <strong>the</strong> head pin in different spots - head on, or on <strong>the</strong> right or left side. A<br />

pin is 4½" in diameter at <strong>the</strong> height at which <strong>the</strong> ball contacts it, and <strong>the</strong> center <strong>of</strong><br />

<strong>the</strong> pin is located 60' ±½" from <strong>the</strong> foul line. A ball is nominally 8½" in diameter.<br />

Assuming <strong>the</strong> ball is released with its center over <strong>the</strong> foul line and it hits <strong>the</strong> head<br />

pin dead center, it must travel 59' 5" to 59' 6" from <strong>the</strong> point <strong>of</strong> release. If <strong>the</strong> ball<br />

barely grazes <strong>the</strong> right or left side <strong>of</strong> <strong>the</strong> head pin, <strong>the</strong> ball traveled at least 59'<br />

11½" to 60' ½". A solid pocket hit (<strong>the</strong> goal <strong>of</strong> any potential strike delivery) falls<br />

halfway between <strong>the</strong>se two ranges, so <strong>the</strong> expected distance from <strong>the</strong> foul line that<br />

<strong>the</strong> initial pin impact should occur is 59' 8¾". There<strong>for</strong>e, <strong>the</strong> margin <strong>of</strong> error<br />

introduced in hitting <strong>the</strong> head pin is ±3¾"<br />

If <strong>the</strong> ball misses <strong>the</strong> head pin, it must travel at least an additional 10.4" to get to<br />

<strong>the</strong> next pin, and <strong>the</strong> same error factors as <strong>for</strong> hitting <strong>the</strong> head pin come into play.<br />

The bowler could take note <strong>of</strong> <strong>the</strong> first pin that was hit - <strong>the</strong> head pin, <strong>the</strong> 2/3 pins,<br />

<strong>the</strong> 4/6 pins or <strong>the</strong> 7/10 pins, and <strong>the</strong> analysis s<strong>of</strong>tware could again adjust <strong>for</strong> <strong>the</strong><br />

difference. Bowlers readily identify <strong>the</strong> location <strong>of</strong> <strong>the</strong> ball based on <strong>the</strong> board it<br />

is on when it hits <strong>the</strong> pins. This in<strong>for</strong>mation could be used to better locate <strong>the</strong> ball<br />

at pin impact, along with <strong>the</strong> first pin hit, and this error could be reduced to<br />

approximately ±1".<br />

55

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