t检验
// 导入数据 "data/data2aitt" , sheet("data2aitt" ) firstrow clear // firstrow: treat first row of Excel data as variable names
___ ____ ____ ____ ____ ©
/__ / ____/ / ____/ 17.0
___/ / /___/ / /___/ BE—Basic Edition
Statistics and Data Science Copyright 1985-2021 StataCorp LLC
StataCorp
4905 Lakeway Drive
College Station, Texas 77845 USA
800-STATA-PC https://www.stata.com
979-696-4600 stata@stata.com
Stata license: Single-user perpetual
Serial number: 301706350312
Licensed to: Clinical Research Center
Maoming People's Hospital
Notes:
1. Unicode is supported; see help unicode_advice.
(54 vars, 240 obs)
Contains data
Observations: 240
Variables: 54
-------------------------------------------------------------------------------
Variable Storage Display Value
name type format label Variable label
-------------------------------------------------------------------------------
Group byte %10.0g Group
ID int %10.0g ID
Comorbidity byte %10.0g Comorbidity
Age byte %10.0g Age
Height double %10.0g Height
Weight double %10.0g Weight
BMI double %10.0g BMI
Gender byte %10.0g Gender
Education byte %10.0g Education
Smoking byte %10.0g Smoking
Ysmoking byte %10.0g Ysmoking
Drinking byte %10.0g Drinking
Ydrinking byte %10.0g Ydrinking
Allergy byte %10.0g Allergy
Tem double %10.0g Tem
HR int %10.0g HR
RR byte %10.0g RR
SBP int %10.0g SBP
DBP int %10.0g DBP
BCSS0 byte %10.0g BCSS0
BCSS1 byte %10.0g BCSS1
BCSS2 byte %10.0g BCSS2
BCSS3 double %10.0g BCSS3
BCSS4 byte %10.0g BCSS4
BCSS5 double %10.0g BCSS5
VASB0 double %10.0g VASB0
VASB1 double %10.0g VASB1
VASB2 double %10.0g VASB2
VASB3 double %10.0g VASB3
VASB4 double %10.0g VASB4
VASB5 double %10.0g VASB5
VASC0 double %10.0g VASC0
VASC1 double %10.0g VASC1
VASC2 double %10.0g VASC2
VASC3 double %10.0g VASC3
VASC4 double %10.0g VASC4
VASC5 double %10.0g VASC5
Hospitaldurat~n byte %10.0g Hospital duration
Death byte %10.0g Death
CB1 byte %10.0g CB1
CB2 byte %10.0g CB2
CB3 double %10.0g CB3
CB4 byte %10.0g CB4
CB5 double %10.0g CB5
CVASB1 double %10.0g CVASB1
CVASB2 double %10.0g CVASB2
CVASB3 double %10.0g CVASB3
CVASB4 double %10.0g CVASB4
CVASB5 double %10.0g CVASB5
CVASC1 double %10.0g CVASC1
CVASC2 double %10.0g CVASC2
CVASC3 double %10.0g CVASC3
CVASC4 double %10.0g CVASC4
CVASC5 double %10.0g CVASC5
-------------------------------------------------------------------------------
Sorted by:
Note: Dataset has changed since last saved.
// 检验各个变量之间的差异，by group name ttest BCSS0, by (Group)ttest BCSS1, by (Group)ttest BCSS2, by (Group)ttest BCSS3, by (Group)ttest BCSS4, by (Group)ttest BCSS5, by (Group)
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 5.625 .1806704 1.979145 5.267254 5.982746
1 | 120 5.816667 .1782986 1.953163 5.463618 6.169716
---------+--------------------------------------------------------------------
Combined | 240 5.720833 .1268033 1.964428 5.471039 5.970628
---------+--------------------------------------------------------------------
diff | -.1916667 .253835 -.6917169 .3083835
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = -0.7551
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.2255 Pr(|T| > |t|) = 0.4509 Pr(T > t) = 0.7745
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 5.075 .1795429 1.966794 4.719487 5.430513
1 | 120 4.966667 .1714714 1.878375 4.627136 5.306197
---------+--------------------------------------------------------------------
Combined | 240 5.020833 .1239247 1.919832 4.776709 5.264957
---------+--------------------------------------------------------------------
diff | .1083333 .2482702 -.3807543 .597421
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 0.4364
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.6685 Pr(|T| > |t|) = 0.6630 Pr(T > t) = 0.3315
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 4.458333 .1738894 1.904863 4.114015 4.802652
1 | 120 3.9 .1624394 1.779434 3.578354 4.221646
---------+--------------------------------------------------------------------
Combined | 240 4.179167 .1200953 1.860508 3.942586 4.415747
---------+--------------------------------------------------------------------
diff | .5583333 .2379581 .0895602 1.027106
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 2.3464
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.9901 Pr(|T| > |t|) = 0.0198 Pr(T > t) = 0.0099
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 3.820833 .1588646 1.740274 3.506266 4.135401
1 | 120 2.941667 .1431419 1.568041 2.658231 3.225102
---------+--------------------------------------------------------------------
Combined | 240 3.38125 .11042 1.710619 3.163729 3.598771
---------+--------------------------------------------------------------------
diff | .8791667 .21384 .4579057 1.300428
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 4.1113
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 1.0000 Pr(|T| > |t|) = 0.0001 Pr(T > t) = 0.0000
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 3.175 .1590688 1.742511 2.860028 3.489972
1 | 120 2.241667 .1405251 1.539376 1.963413 2.51992
---------+--------------------------------------------------------------------
Combined | 240 2.708333 .110121 1.705987 2.491402 2.925265
---------+--------------------------------------------------------------------
diff | .9333333 .2122503 .5152042 1.351462
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 4.3973
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 1.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 0.0000
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 2.798333 .1599106 1.751733 2.481694 3.114972
1 | 120 1.591667 .1180466 1.293135 1.357923 1.825411
---------+--------------------------------------------------------------------
Combined | 240 2.195 .1065755 1.65106 1.985053 2.404947
---------+--------------------------------------------------------------------
diff | 1.206667 .1987622 .8151089 1.598224
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 6.0709
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 1.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 0.0000
// generate new variable gen deltaBCSS1 = BCSS1-BCSS0gen deltaBCSS2 = BCSS2-BCSS0 gen deltaBCSS3 = BCSS3-BCSS0gen deltaBCSS4 = BCSS4-BCSS0gen deltaBCSS5 = BCSS5-BCSS0
ttest deltaBCSS1, by (Group)ttest deltaBCSS2, by (Group)ttest deltaBCSS3, by (Group)ttest deltaBCSS4, by (Group)ttest deltaBCSS5, by (Group)
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 -.55 .0718405 .7869738 -.6922515 -.4077485
1 | 120 -.85 .1015634 1.112571 -1.051106 -.6488943
---------+--------------------------------------------------------------------
Combined | 240 -.7 .0628252 .9732833 -.8237618 -.5762382
---------+--------------------------------------------------------------------
diff | .3 .1244033 .0549277 .5450723
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 2.4115
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.9917 Pr(|T| > |t|) = 0.0166 Pr(T > t) = 0.0083
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 -1.166667 .1040721 1.140053 -1.37274 -.9605935
1 | 120 -1.916667 .1383088 1.515097 -2.190532 -1.642801
---------+--------------------------------------------------------------------
Combined | 240 -1.541667 .0897058 1.389716 -1.718382 -1.364952
---------+--------------------------------------------------------------------
diff | .75 .1730905 .4090149 1.090985
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 4.3330
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 1.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 0.0000
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 -1.804167 .1197125 1.311385 -2.041209 -1.567124
1 | 120 -2.875 .1541047 1.688132 -3.180143 -2.569857
---------+--------------------------------------------------------------------
Combined | 240 -2.339583 .1033415 1.600959 -2.54316 -2.136007
---------+--------------------------------------------------------------------
diff | 1.070833 .1951393 .6864126 1.455254
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 5.4875
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 1.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 0.0000
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 -2.45 .1182565 1.295435 -2.68416 -2.21584
1 | 120 -3.575 .155056 1.698554 -3.882026 -3.267974
---------+--------------------------------------------------------------------
Combined | 240 -3.0125 .103879 1.609286 -3.217135 -2.807865
---------+--------------------------------------------------------------------
diff | 1.125 .195005 .7408437 1.509156
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 5.7691
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 1.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 0.0000
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. err. Std. dev. [95% conf. interval]
---------+--------------------------------------------------------------------
0 | 120 -2.826667 .1390833 1.523581 -3.102065 -2.551268
1 | 120 -4.225 .161602 1.770261 -4.544988 -3.905012
---------+--------------------------------------------------------------------
Combined | 240 -3.525833 .1155968 1.790818 -3.753552 -3.298115
---------+--------------------------------------------------------------------
diff | 1.398333 .213212 .9783096 1.818357
------------------------------------------------------------------------------
diff = mean(0) - mean(1) t = 6.5584
H0: diff = 0 Degrees of freedom = 238
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 1.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 0.0000
回归
Source | SS df MS Number of obs = 74
-------------+---------------------------------- F(1, 72) = 20.26
Model | 139449474 1 139449474 Prob > F = 0.0000
Residual | 495615923 72 6883554.48 R-squared = 0.2196
-------------+---------------------------------- Adj R-squared = 0.2087
Total | 635065396 73 8699525.97 Root MSE = 2623.7
------------------------------------------------------------------------------
price | Coefficient Std. err. t P>|t| [95% conf. interval]
-------------+----------------------------------------------------------------
mpg | -238.8943 53.07669 -4.50 0.000 -344.7008 -133.0879
_cons | 11253.06 1170.813 9.61 0.000 8919.088 13587.03
------------------------------------------------------------------------------
To get standardized coefficients we add the beta option to our command.
Source | SS df MS Number of obs = 74
-------------+---------------------------------- F(1, 72) = 20.26
Model | 139449474 1 139449474 Prob > F = 0.0000
Residual | 495615923 72 6883554.48 R-squared = 0.2196
-------------+---------------------------------- Adj R-squared = 0.2087
Total | 635065396 73 8699525.97 Root MSE = 2623.7
------------------------------------------------------------------------------
price | Coefficient Std. err. t P>|t| Beta
-------------+----------------------------------------------------------------
mpg | -238.8943 53.07669 -4.50 0.000 -.4685967
_cons | 11253.06 1170.813 9.61 0.000 .
------------------------------------------------------------------------------
Visualizing Regression Lines
graph twoway scatter price mpg
Add the regression line to the plot. The lfit graph command allows us to do this (lfit stands for linear fit). However, we don’t want the regression line in isolation. We want it on top of the scatterplot. Stata lets you combine twoway graphs in one of two ways: (1) using parentheses or (2) using pipes.
graph twoway (lfit price mpg) (scatter price mpg)
graph twoway lfitci price mpg || scatter price mpg
关联
weight length
(obs=74)
| price mpg weight length
-------------+------------------------------------
price | 1.0000
mpg | -0.4686 1.0000
weight | 0.5386 -0.8072 1.0000
length | 0.4318 -0.7958 0.9460 1.0000
corr price mpg weigh length , covariance
(obs=74)
| price mpg weight length
-------------+------------------------------------
price | 8.7e+06
mpg | -7996.28 33.472
weight | 1.2e+06 -3629.43 604030
length | 28360.3 -102.514 16370.9 495.79
pwcorr price mpg weight length , sig
| price mpg weight length
-------------+------------------------------------
price | 1.0000
|
|
mpg | -0.4686 1.0000
| 0.0000
|
weight | 0.5386 -0.8072 1.0000
| 0.0000 0.0000
|
length | 0.4318 -0.7958 0.9460 1.0000
| 0.0001 0.0000 0.0000
|
