Linear regression (OLS)
 Data     : diamonds
 Response variable    : price
 Explanatory variables: carat, clarity
 Null hyp.: the effect of x on price is zero
 Alt. hyp.: the effect of x on price is not zero

 coefficient std.error t.value p.value
 (Intercept)    -6780.993   204.952 -33.086  < .001 ***
 carat           8438.030    51.101 165.125  < .001 ***
 clarity|SI2     2790.760   201.395  13.857  < .001 ***
 clarity|SI1     3608.531   200.508  17.997  < .001 ***
 clarity|VS2     4249.906   201.607  21.080  < .001 ***
 clarity|VS1     4461.956   204.592  21.809  < .001 ***
 clarity|VVS2    5109.476   210.207  24.307  < .001 ***
 clarity|VVS1    5027.669   214.251  23.466  < .001 ***
 clarity|IF      5265.170   233.658  22.534  < .001 ***

 Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

 R-squared: 0.904,  Adjusted R-squared: 0.904
 F-statistic: 3530.024 df(8,2991), p.value < .001
 Nr obs: 3,000