
657 P.2d 1157 (1983)
Joseph Lewis McCULLOUGH, Appellant,
v.
The STATE of Nevada, Respondent.
No. 13838.
Supreme Court of Nevada.
February 10, 1983.
Thomas E. Perkins, State Public Defender, Annabelle Whiting Hall, Deputy Public Defender, Carson City, for appellant.
Brian McKay, Atty. Gen., Dan R. Reaser, Deputy Atty. Gen., Carson City, Virginia R. Shane, Dist. Atty., Jack T. Bullock, II, Deputy Dist. Atty., Winnemucca, for respondent.

OPINION
PER CURIAM:
A jury found appellant Joseph Lewis McCullough guilty of possession of a controlled substance and possession of stolen property. Among other contentions, McCullough argues on appeal that the jury was prejudicially misinformed regarding the concept of reasonable doubt, because the district judge made several attempts to quantify reasonable doubt during the voir dire examination of the jurors and also delivered an improper jury instruction on the subject. A review of the authorities and the record leads us to agree with appellant, and we therefore reverse.

THE FACTS
McCullough was charged with possession of a controlled substance (marijuana) and possession of stolen property (a 1974 Chevrolet "Luv" pickup truck).
During the voir dire examination of the jurors during trial, the district judge attempted to illustrate the concept of reasonable doubt with a numerical scale. On a scale of zero to ten, the judge placed the preliminary hearing standard of probable cause at about one, and the burden of persuasion in civil trials at just over five. He then twice described reasonable doubt as about "seven and a half, if you had to put it on a scale." After introducing the jurors to the reasonable doubt standard provided by NRS 175.211, the judge again noted, "I have tried to give you that on a zero to ten scale."
*1158 The district judge further embellished the statutory definition of reasonable doubt in his instructions to the jury, stating in instruction number five that "it is not necessary that the defendant's guilt should be established beyond any doubt or to an absolute certainty... ." McCullough's trial counsel did not object to the judge's extemporaneous characterizations of reasonable doubt, nor did she object to the above instruction.[1]

FAILURE TO OBJECT
The general rule is that failure to object to asserted errors at trial will bar review of an issue on appeal. Krueger v. State, 92 Nev. 749, 755, 557 P.2d 717, 721 (1976); Walker v. State, 89 Nev. 568, 516 P.2d 739 (1973); Clark v. State, 89 Nev. 392, 513 P.2d 1224 (1973). However, when constitutional questions are raised on appeal, we have the power to address them. Dias v. State, 95 Nev. 710, 601 P.2d 706 (1979); Hardison v. State, 84 Nev. 125, 437 P.2d 868 (1968). We believe that the issues in this case are of constitutional dimension. See Dunn v. Perrin, 570 F.2d 21, 25 (1st Cir.1978).

DEFINING REASONABLE DOUBT
In NRS 175.211, the Legislature has both defined reasonable doubt and mandated that no other definition shall be given to juries in criminal actions in Nevada.[2] Despite our frequent condemnations of the practice, the lower courts of this state have persisted in adding to the statutory reasonable doubt definition. See, e.g., Page v. State, 94 Nev. 386, 580 P.2d 477 (1978); Jackson v. State, 93 Nev. 677, 572 P.2d 927 (1977); Tucker v. State, 92 Nev. 486, 553 P.2d 951 (1976). Instruction number five in this case is identical to the supplemental instruction disapproved in Page and Jackson, where we held that, standing alone, the instruction was not reversible error.[3] We now hold that the disapproved instruction is reversible error when coupled with any other attempt to supplement, change, or clarify the statutory reasonable doubt definition.
In the instant case, the district judge tried to edify the jury by placing the reasonable doubt concept on a numerical scale. While an attempt by the trial court to clarify the meaning of reasonable doubt is not by itself reversible error, see Page v. State and Jackson v. State, supra, the question on appeal is whether the court's statements correctly conveyed the concept of reasonable doubt to the jury. Holland v. United States, 348 U.S. 121, 140, 75 S.Ct. 127, 137, 99 L.Ed. 150 (1954); State v. Olivera, 57 Hawaii 339, 555 P.2d 1199 (1976).
The U.S. Supreme Court has stated that the reasonable doubt instruction should impress on the jury the need to reach a "subjective state of near certitude" on the facts in issue. Jackson v. Virginia, 443 U.S. 307, 315, 99 S.Ct. 2781, 2787, 61 L.Ed.2d 560 (1970). See In re Winship, 397 U.S. 358, 364, 90 S.Ct. 1068, 1072, 25 L.Ed.2d 368 (1970). For example, where a trial court had punctuated the statutory reasonable doubt definition with statements to the effect that the state was not required to establish guilt "beyond all doubt," to an "absolute positive certainty," to a "mathematical certainty," or to a "scientific certainty," the judgment was reversed on the grounds that the instruction impermissibly *1159 favored the prosecution. State v. Aubert, 120 N.H. 634, 421 A.2d 124 (1980).
The concept of reasonable doubt is inherently qualitative. Any attempt to quantify it may impermissibly lower the prosecution's burden of proof, and is likely to confuse rather than clarify. See Dunn v. Perrin, 570 F.2d 21, 23 (1st Cir.1978). As one Second Circuit panel noted, "[t]he heart of [the reasonable doubt charge] was appropriate enough, but the somewhat confusing parable of the father and a bundle of twigs and the apparent characterization of the standard as quantitative rather than qualitative both might better have been omitted." United States v. Anglada, 524 F.2d 296, 300 (2d Cir.1975).
In this case the district court may have led the jury to believe that the prosecution satisfied the burden established by In re Winship if the proof reached a score of 7.5 on a scale of zero to ten. Alternatively, the jury may improperly have concluded that anything more than a 75% chance of each fact being true was constitutionally sufficient to find McCullough guilty as charged. The judge's numerical description of reasonable doubt, particularly because it was coupled with a reasonable doubt instruction that deviated from the command of NRS 175.211, constituted prejudicial error. In light of our treatment of this issue, we need not discuss appellant's other contentions. Reversed and remanded for a new trial.
NOTES
[1]  McCullough's counsel on appeal did not represent McCullough in the district court.
[2]  NRS 175.211. Reasonable doubt defined; no other definition to be given to juries.

1. A reasonable doubt is one based on reason. It is not mere possible doubt, but is such a doubt as would govern or control a person in the more weighty affairs of life. If the minds of the jurors, after the entire comparison and consideration of all the evidence, are in such a condition that they can say they feel an abiding conviction of the truth of the charge, there is not a reasonable doubt. Doubt to be reasonable must be actual and substantial, not mere possibility or speculation.
2. No other definition of reasonable doubt shall be given by the court to juries in criminal actions in this state.
[3]  Instruction Number Five stated as follows:

"It is not necessary that the defendant's guilt should be established beyond any doubt or to an absolute certainty, but instead thereof that the defendant's guilt must be established beyond a reasonable doubt as hereinafter defined."
