Two Sample T-Test

twosamplet calculates a two sample t-test and/or interval from summary data. It defaults to a hypothesized population mean difference of 0. You can optionally set an alternative hypothesis and confidence level for a two-sided confidence interval.

Usage

iscamtwosamplet(
  x1,
  sd1,
  n1,
  x2,
  sd2,
  n2,
  hypothesized = 0,
  alternative = NULL,
  conf.level = 0
)

Arguments

x1

Observed mean for group 1.

sd1

Observed standard deviation for group 1.

n1

Sample size for group 1.

x2

Observed mean for group 2.

sd2

Observed standard deviation for group 2.

n2

Sample size for group 2.

hypothesized

Hypothesized difference in population means.

alternative

"less", "greater", or "two.sided"

conf.level

Confidence level.

Value

The t value, p value, and confidence interval.

Examples

iscamtwosamplet(
  x1 = 25,
  sd1 = 5,
  n1 = 40,
  x2 = 22,
  sd2 = 6,
  n2 = 45,
  alternative = "greater"
)
#> 
#> Two Sample t test
#> 
#> Group1: mean = 25, sd = 5,  sample size = 40
#> Group2: mean = 22, sd = 6,  sample size = 45
#> diff:3
#> 
#> Null hypothesis       : mu1-mu2 = 0 
#> Alternative hypothesis: mu1-mu2 > 0 
#> t-statistic: 2.513 
#> df: 82.68 

#> p-value: 0.006954 
iscamtwosamplet(
  x1 = 10,
  sd1 = 2,
  n1 = 50,
  x2 = 12,
  sd2 = 2.5,
  n2 = 50,
  alternative = "two.sided"
)
#> 
#> Two Sample t test
#> 
#> Group1: mean = 10, sd = 2,  sample size = 50
#> Group2: mean = 12, sd = 2.5,  sample size = 50
#> diff:-2
#> 
#> Null hypothesis       : mu1-mu2 = 0 
#> Alternative hypothesis: mu1-mu2 <> 0 
#> t-statistic: -4.417 
#> df: 93.49 

#> p-value: 2.686e-05 
iscamtwosamplet(
  x1 = 8,
  sd1 = 1.5,
  n1 = 30,
  x2 = 5,
  sd2 = 1.8,
  n2 = 33,
  alternative = "greater",
  hypothesized = 2
)
#> 
#> Two Sample t test
#> 
#> Group1: mean = 8, sd = 1.5,  sample size = 30
#> Group2: mean = 5, sd = 1.8,  sample size = 33
#> diff:3
#> 
#> Null hypothesis       : mu1-mu2 = 2 
#> Alternative hypothesis: mu1-mu2 > 2 
#> t-statistic: 2.403 
#> df: 60.56 

#> p-value: 0.009671 
iscamtwosamplet(
  x1 = 15,
  sd1 = 3,
  n1 = 25,
  x2 = 12,
  sd2 = 3.5,
  n2 = 28,
  conf.level = 0.95
)
#> 
#> Two Sample t test
#> 
#> Group1: mean = 15, sd = 3,  sample size = 25
#> Group2: mean = 12, sd = 3.5,  sample size = 28
#> diff:3
#> 
#> 95 % Confidence interval for mu1-mu2: ( 1.207102 ,  4.792898 )