A ESCOLHA DO MÉTODO ESTATÍSTICO - SBPqO

Delineamento inteiramente aleatorizado
Esquema da análise de variância:
Fonte de
variação
Graus de
liberdade
Soma de Quadrados Quadrado médio F
Tratamento I – 1
Variabilidade devido
ao tratamento
Resíduo I (J – 1) Por diferença
SQ tratamento
GL trat.
SQ resíduo
GL resíduo
QM tratamento
QM resíduo
-
Total IJ – 1 Variabilidade total - -
I = número de níveis do tratamento
J = número de repetições
Poder estatístico
Reviewer: What were criteria for sample size selection? Was
it to reach estimated power (80%)?
The sample size selection was based on a pilot study, made with 3 volunteers,
who ingested the 550 µg F/g dentifrice, on fasting, after breakfast or after
lunch, and we used the AUC of salivary F concentration as the response
variable. In fact, we intended to determine the number of volunteers necessary
to detect differences between the gastric content
situations using the low F
dentifrice, with 80% power. From this pilot study, a low standard deviation was
observed between volunteers for each gastric content condition. Using the
SAS System 8.01, considering the differences obtained from the mean of these
treatments, we could reach 80% power if we used nine volunteers. For 11
volunteers, the power would increase to 90%. Considering that volunteers
could be lost during the 9-phase study, we opted to select 11 volunteers.
Actually, we could significantly reject H 0 in the experiment, and therefore we
haven’t
worried in mention this in the text, but we added the power
information in the text.
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