Table 7.

Comparing N2 and N3 across spindle features

	$\beta$ original	t original	$\beta$ rankit	t rankit
Density (min−1)	−0.396	−9.186*	−0.384	−13.191*
Amplitude (µV)	1.15	1.351	0.05	1.486
Frequency (Hz)	−0.084	−5.942*	−0.178	−8.916*
Interspindle SD (Hz)	−0.053	−6.166*	−0.289	−8.425*
Intraspindle SD (Hz)	−0.005	−0.973	−0.012	−0.452
Frequency range (Hz)	−0.053	−3.322*	−0.108	−3.54*
Frequency change (Hz/s)	−0.006	−0.227	0.044	1.001
Duration (s)	−0.023	−9.183*	−0.47	−12.235*
Rise-decay symmetry	4e-04	0.56	0.062	1.766
Peak-trough symmetry	0.002	2.746*	0.054	2.48*

The first two columns correspond to the estimated difference in a LMEM for each spindle measure between N2 and N3 and significance of this estimate (N2 is reference). The next two columns represent the difference after rank inverse normal transformation of the data (rankit) followed by implementing a robust LMEM, which mitigates the effect of outliers on parameter estimates. All measures show no change in significance after transformation (with p < 0.05 as |t| > 1.96). An asterisk indicates significant after correction for multiple comparisons via FDR (p < 0.05); the $\beta$ estimates in column 1 are in natural units whereas the estimates in column 3 are normalized. QQ plots before and after transformation are shown in Extended Data Table 7-1.