Table 2

Summary of Study Populations

Study	Year	Symptomatic/Asymptomatic	Total Sample Size	Males	Females	Age Range (yrs)
Tanz	1953	Asymptomatic	55	17	38	10 Children, 45 Adults (2-77 years)
Clayson	1962	Asymptomatic	26	0	26	College Age
Froning	1968	Symptomatic but “Normal” by authors’ definition	30	unknown	unknown	unknown
Hayes	1986	Asymptomatic	59	59	0	19-59
Dvorak	1991	Asymptomatic	41	23	18	22-50
Frobin	1996	Asymptomatic	61	45	16	19-57